* Added support for "fast" (64-clock) refresh
authorSteven J. Magnani <steve@digidescorp.com>
Mon, 26 Sep 2005 13:54:32 +0000 (13:54 +0000)
committerSteven J. Magnani <steve@digidescorp.com>
Mon, 26 Sep 2005 13:54:32 +0000 (13:54 +0000)
* Added code to support remap window for 3 - 4 GB systems
* Fixed premature configuration of true row boundaries that resulted in some sections of DRAM not receiving JEDEC commands (see http://openbios.org/pipermail/linuxbios/2005-June/011752.html).
* Redefined RCOMP_MMIO so that RCOMP registers can be configured on systems where A20M# is asserted.
* Disabled subsystem (vendor) ID configuration
* #ifdef'd out suspicious looking code (see http://openbios.org/pipermail/linuxbios/2005-June/011759.html)
* Added optional run-time checking of dual-channel compatibility of installed DIMMs
* Move JEDEC SPD and SDRAM definitions into reusable #include files

git-svn-id: svn://svn.coreboot.org/coreboot/trunk@2048 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

src/northbridge/intel/e7501/raminit.c

index 06cabe3953c6fdcd2bb41d88a34e8953f84674ba..d8b8a723e1c385303ab1ec5a3daaa34024e9f621 100644 (file)
@@ -1,4 +1,3 @@
-
 /* This was originally for the e7500, modified for e7501
  * The primary differences are that 7501 apparently can 
  * support single channel RAM (i haven't tested),
 
 /* converted to C 6/2004 yhlu */
 
-#define DEBUG_RAM_CONFIG 0
-
-#define dumpnorth() dump_pci_device(PCI_DEV(0, 0, 0)) 
-
-/* DDR DIMM Mode register Definitions */
-
-#define BURST_2           (1<<0)
-#define BURST_4           (2<<0)
-#define BURST_8           (3<<0)
-
-#define BURST_SEQUENTIAL  (0<<3)
-#define BURST_INTERLEAVED (1<<3)
-
-#define CAS_2_0                  (0x2<<4)
-#define CAS_3_0           (0x3<<4)
-#define CAS_1_5           (0x5<<4)
-#define CAS_2_5           (0x6<<4)
-
-#define MODE_NORM         (0 << 7)
-#define MODE_DLL_RESET    (2 << 7)
-#define MODE_TEST         (1 << 7)
-
-#define BURST_LENGTH BURST_4
-#define BURST_TYPE   BURST_INTERLEAVED
-#define CAS_LATENCY  CAS_2_0
-//#define CAS_LATENCY  CAS_2_5
-//#define CAS_LATENCY  CAS_1_5
+#include <assert.h>
+#include <spd.h>
+#include <sdram_mode.h>
+#include "e7501.h"
 
-#define MRS_VALUE (MODE_NORM | CAS_LATENCY | BURST_TYPE | BURST_LENGTH)
-#define EMRS_VALUE 0x000
+// Uncomment this to enable run-time checking of DIMM parameters 
+// for dual-channel operation
+// Unfortunately the code seems to chew up several K of space.
+//#define VALIDATE_DIMM_COMPATIBILITY
 
-#define MD_SHIFT 4
+// Uncomment this to enable local debugging messages
+//#define DEBUG_RAM_CONFIG
 
-#define RAM_COMMAND_NONE       0x0
-#define RAM_COMMAND_NOP                0x1
-#define RAM_COMMAND_PRECHARGE  0x2
-#define RAM_COMMAND_MRS                0x3
-#define RAM_COMMAND_EMRS       0x4
-#define RAM_COMMAND_CBR                0x6
-#define RAM_COMMAND_NORMAL     0x7
-
-
-static inline void do_ram_command (const struct mem_controller *ctrl, uint32_t value) {
-        uint32_t dword;
-        uint8_t byte;
-        int i;
-        uint32_t result;
-#if DEBUG_RAM_CONFIG >= 2
-        print_debug("P:");
-        print_debug_hex8(value);
-        print_debug("\r\n");
-#endif
-        /* %ecx - initial address to read from */
-        /* Compute the offset */
-        dword = value >> 16;
-        for(i=0;i<8;i++) {
-                /* Set the ram command */
-                byte = pci_read_config8(ctrl->d0, 0x7c);
-                byte &= 0x8f;
-                byte |= (uint8_t)(value & 0xff);
-                pci_write_config8(ctrl->d0, 0x7c, byte);
-
-                /* Assert the command to the memory */
-#if DEBUG_RAM_CONFIG  >= 2
-                print_debug("R:");
-                print_debug_hex32(dword);
-                print_debug("\r\n");
+#if defined(DEBUG_RAM_CONFIG)
+#define RAM_DEBUG_MESSAGE(x)   print_debug(x)
+#define RAM_DEBUG_HEX32(x)             print_debug_hex32(x)
+#define RAM_DEBUG_HEX8(x)              print_debug_hex8(x)
+#define DUMPNORTH()                            dump_pci_device(PCI_DEV(0, 0, 0))
+#else
+#define RAM_DEBUG_MESSAGE(x)
+#define RAM_DEBUG_HEX32(x)
+#define RAM_DEBUG_HEX8(x)
+#define DUMPNORTH()
 #endif
 
-                result = read32(dword);
-
-                /* Go to the next base address */
-                dword += 0x04000000;
-
-        } 
-
-        /* The command has been sent to all dimms so get out */
-}
-
-
-static inline void RAM_CMD(const struct mem_controller *ctrl, uint32_t command, uint32_t offset)  {
-       uint32_t value =        ((offset) << (MD_SHIFT + 16))|((command << 4) & 0x70) ; 
-       do_ram_command(ctrl, value);
-}
-       
-#define RAM_NOP(ctrl)          RAM_CMD(ctrl, RAM_COMMAND_NOP, 0)
-#define RAM_PRECHARGE(ctrl)            RAM_CMD(ctrl, RAM_COMMAND_PRECHARGE, 0)
-#define RAM_CBR(ctrl)          RAM_CMD(ctrl, RAM_COMMAND_CBR, 0)
-#define RAM_EMRS(ctrl)         RAM_CMD(ctrl, RAM_COMMAND_EMRS, EMRS_VALUE)
-
-static const uint8_t ram_cas_latency[] = {
-       CAS_2_5, CAS_2_0, CAS_1_5, CAS_2_5
-       };
-
-static inline void ram_mrs(const struct mem_controller *ctrl, uint32_t value){
-       /* Read the cas latency setting */
-       uint8_t byte;
-       uint32_t dword;
-       byte = pci_read_config8(ctrl->d0, 0x78); 
-       /* Transform it into the form expected by SDRAM */
-       dword = ram_cas_latency[(byte>>4) & 3];
-
-       value  |= (dword<<(16+MD_SHIFT));
-       
-       value |= (MODE_NORM | BURST_TYPE | BURST_LENGTH) << (16+MD_SHIFT);
-
-       do_ram_command(ctrl, value);
-}
-
-#define RAM_MRS(ctrl, dll_reset) ram_mrs( ctrl, (dll_reset << (8+MD_SHIFT+ 16)) | ((RAM_COMMAND_MRS <<4)& 0x70) )
+#define E7501_SDRAM_MODE       (SDRAM_BURST_INTERLEAVED | SDRAM_BURST_4)
+#define SPD_ERROR                      "Error reading SPD info\r\n"
 
-static void RAM_NORMAL(const struct mem_controller *ctrl) {
-       uint8_t byte;
-       byte = pci_read_config8(ctrl->d0, 0x7c);
-       byte &=  0x8f;
-       byte |= (RAM_COMMAND_NORMAL << 4);
-       pci_write_config8(ctrl->d0, 0x7c, byte);
-}
+// NOTE: This used to be 0x100000.
+//              That doesn't work on systems where A20M# is asserted, because
+//              attempts to access 0x1000NN end up accessing 0x0000NN.
+#define RCOMP_MMIO 0x200000
 
-static void  RAM_RESET_DDR_PTR(const struct mem_controller *ctrl) {
-       uint8_t byte;
-       byte = pci_read_config8(ctrl->d0, 0x88);
-       byte |= (1 << 4 );
-       pci_write_config8(ctrl->d0, 0x88, byte);
-       byte = pci_read_config8(ctrl->d0, 0x88);
-       byte &= ~(1 << 4);
-       pci_write_config8(ctrl->d0, 0x88, byte);
-}
+struct dimm_size {
+        unsigned long side1;
+        unsigned long side2;
+};
 
-static void ENABLE_REFRESH(const struct mem_controller *ctrl) 
-{
-       uint32_t dword;
-       dword = pci_read_config32(ctrl->d0, 0x7c);
-       dword |= (1 << 29);
-       pci_write_config32(ctrl->d0, 0x7c, dword);
-}
+/*^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^*/
+/*                                                                     DEFINITIONS                                                                       */
+/**********************************************************************************/
+
+static const uint32_t refresh_frequency[]= {
+       /* Relative frequency (array value) of each E7501 Refresh Mode Select 
+        * (RMS) value (array index)
+        * 0 == least frequent refresh (longest interval between refreshes)
+        * [0] disabled  -> 0 
+        * [1] 15.6 usec -> 2
+        * [2]  7.8 usec -> 3
+        * [3] 64   usec -> 1
+        * [4] reserved  -> 0
+        * [5] reserved  -> 0
+        * [6] reserved  -> 0
+        * [7] 64 clocks -> 4
+        */
+       0, 2, 3, 1, 0, 0, 0, 4 };
+
+static const uint32_t refresh_rate_map[] = {
+       /* Map the JEDEC spd refresh rates (array index) to E7501 Refresh Mode 
+        * Select values (array value)
+        * These are all the rates defined by JESD21-C Appendix D, Rev. 1.0
+        * The E7501 supports only 15.6 us (1), 7.8 us (2), 64 us (3), and 
+        * 64 clock (481 ns) (7) refresh.
+        * [0] ==  15.625 us -> 15.6 us
+        * [1] ==   3.9   us -> 481  ns
+        * [2] ==   7.8   us ->  7.8 us
+        * [3] ==  31.3   us -> 15.6 us
+        * [4] ==  62.5   us -> 15.6 us
+        * [5] == 125     us -> 64   us
+        */
+       1, 7, 2, 1, 1, 3
+};
+#define MAX_SPD_REFRESH_RATE ((sizeof(refresh_rate_map) / sizeof(uint32_t)) - 1)
+
+
+// SPD parameters that must match for dual-channel operation
+static const uint8_t dual_channel_parameters[] = {
+       SPD_MEMORY_TYPE, 
+       SPD_MODULE_VOLTAGE, 
+       SPD_NUM_COLUMNS, 
+       SPD_NUM_ROWS, 
+       SPD_NUM_DIMM_BANKS, 
+       SPD_PRIMARY_DRAM_WIDTH, 
+       SPD_NUM_BANKS_PER_DRAM
+};
 
        /*
         * Table:       constant_register_values
         */
-static const long register_values[] = {
+static const long constant_register_values[] = {
        /* SVID - Subsystem Vendor Identification Register
         * 0x2c - 0x2d
         * [15:00] Subsytem Vendor ID (Indicates system board vendor)
@@ -161,10 +109,13 @@ static const long register_values[] = {
         * 0x2e - 0x2f
         * [15:00] Subsystem ID
         */
-//      0x2c, 0, (0x15d9 << 0) | (0x3580 << 16),
+        // Not everyone wants to be Super Micro Computer, Inc.
+        // The mainboard should set this if desired.
+        // 0x2c, 0, (0x15d9 << 0) | (0x3580 << 16),            
 
        /* Undocumented
-        * 0x80 - 0x80
+        * (DRAM Read Timing Control, if similar to 855PM?)
+        * 0x80 - 0x81
         * This register has something to do with CAS latencies,
         * possibily this is the real chipset control.
         * At 0x00 CAS latency 1.5 works.
@@ -179,22 +130,9 @@ static const long register_values[] = {
         * work at all.
         * Steven James 02/06/2003
         */
-#if CAS_LATENCY == CAS_2_5
-//     0x80, 0xfffffe00, 0x06 /* Intel E7500 recommended */
-       0x80, 0xfffff000, 0x0662, /* from Factory Bios */
-#elif CAS_LATENCY == CAS_2_0
-//     0x80, 0xfffffe00, 0x0d /* values for register 0x80 */
-       0x80, 0xfffff000, 0x0bb1, /* values for register 0x80 */
-/*
-000 = HI_A Stop Grant generated after 1 Stop Grant
-001 = HI_A Stop Grant generated after 2 Stop Grant
-010 = HI_A Stop Grant generated after 3 Stop Grant
-011 = HI_A Stop Grant generated after 4 Stop Grant*/
-       0x50, 0xffff1fff, 0x00006000, 
-#endif
-
-       /* Enable periodic memory recalibration */
-       0x88, 0xffffff00, 0x80,
+    /* NOTE: values now configured in configure_e7501_cas_latency() based 
+        *       on SPD info and total number of DIMMs (per Intel)
+        */
 
        /* FDHC - Fixed DRAM Hole Control
         * 0x58
@@ -223,6 +161,8 @@ static const long register_values[] = {
         *       10 == Write Only (Writes to DRAM, Reads to memory mapped I/O space)
         *       11 == Normal (All Access go to DRAM)
         */
+
+       // Map all legacy ranges to DRAM
        0x58, 0xcccccf7f, (0x00 << 0) | (0x30 << 8) | (0x33 << 16) | (0x33 << 24),
        0x5C, 0xcccccccc, (0x33 << 0) | (0x33 << 8) | (0x33 << 16) | (0x33 << 24),
 
@@ -232,11 +172,12 @@ static const long register_values[] = {
         *     memory address assigned  to each pair of DIMMS, in 64MB 
         *     granularity.   
         */
-       /* Conservatively say each row has 64MB of ram, we will fix this up later */
+       // Conservatively say each row has 64MB of ram, we will fix this up later
+       // NOTE: These defaults allow us to prime all of the DIMMs on the board
+       //               without jumping through 36-bit adddressing hoops, even if the
+       //               total memory is > 4 GB. Changing these values may break do_ram_command()!
        0x60, 0x00000000, (0x01 << 0) | (0x02 << 8) | (0x03 << 16) | (0x04 << 24),
        0x64, 0x00000000, (0x05 << 0) | (0x06 << 8) | (0x07 << 16) | (0x08 << 24),
-       0x68, 0xffffffff, 0,
-       0x6C, 0xffffffff, 0,
 
        /* DRA - DRAM Row Attribute Register 
         * 0x70 Row 0,1
@@ -247,33 +188,25 @@ static const long register_values[] = {
         *       0 == 8 bits wide x8
         *       1 == 4 bits wide x4
         * [6:4] Row Attributes for Odd numbered rows
-        *       010 == 8KB
-        *       011 == 16KB
-        *       100 == 32KB
-        *       101 == 64KB
+        *       010 == 8KB (for dual-channel)
+        *       011 == 16KB (for dual-channel)
+        *       100 == 32KB (for dual-channel)
+        *       101 == 64KB (for dual-channel)
         *       Others == Reserved
         * [3:3] Device width for Even numbered rows
         *       0 == 8 bits wide x8
         *       1 == 4 bits wide x4
         * [2:0] Row Attributes for Even numbered rows
-        *       010 == 8KB
-        *       011 == 16KB
-        *       100 == 32KB
+        *       010 == 8KB (for dual-channel)
+        *       011 == 16KB (for dual-channel)
+        *       100 == 32KB (for dual-channel)
         *       101 == 64KB (This page size appears broken)
         *       Others == Reserved
         */
-       0x70, 0x00000000, 
-               (((0<<3)|(0<<0))<< 0) | 
-               (((0<<3)|(0<<0))<< 4) | 
-               (((0<<3)|(0<<0))<< 8) | 
-               (((0<<3)|(0<<0))<<12) | 
-               (((0<<3)|(0<<0))<<16) | 
-               (((0<<3)|(0<<0))<<20) | 
-               (((0<<3)|(0<<0))<<24) | 
-               (((0<<3)|(0<<0))<<28),
-       0x74, 0xffffffff, 0,
-
-       /* DRT - DRAM Time Register
+        // NOTE: overridden by configure_e7501_row_attributes(), later
+       0x70, 0x00000000, 0,
+
+       /* DRT - DRAM Timing Register
         * 0x78
         * [31:30] Reserved
         * [29:29] Back to Back Write-Read Turn Around
@@ -294,7 +227,7 @@ static const long register_values[] = {
         * [18:16] DRAM idle timer
         *      000 == infinite
         *      011 == 16 dram clocks
-        *      001 == Datasheet says reserved, but Intel BIOS sets it
+        *      001 == 0 clocks
         * [15:11] Reserved
         * [10:09] Active to Precharge (tRAS)
         *         00 == 7 clocks
@@ -305,7 +238,7 @@ static const long register_values[] = {
         * [05:04] Cas Latency (tCL)
         *         00 == 2.5 Clocks
         *         01 == 2.0 Clocks
-        *         10 == 1.5 Clocks
+        *         10 == Reserved (was 1.5 Clocks for E7500)
         *         11 == Reserved
         * [03:03] Write Ras# to Cas# Delay (tRCD)
         *         0 == 3 DRAM Clocks
@@ -319,23 +252,16 @@ static const long register_values[] = {
         *         0 == 3 DRAM Clocks
         *         1 == 2 DRAM Clocks
         */
-#define DRT_CAS_2_5 (0<<4)
-#define DRT_CAS_2_0 (1<<4)   
-#define DRT_CAS_1_5 (2<<4)
-#define DRT_CAS_MASK (3<<4)
-
-#if CAS_LATENCY == CAS_2_5
-#define DRT_CL DRT_CAS_2_5
-#elif CAS_LATENCY == CAS_2_0
-#define DRT_CL DRT_CAS_2_0
-#elif CAS_LATENCY == CAS_1_5
-#define DRT_CL DRT_CAS_1_5
-#endif
 
+        // Some earlier settings:
        /* Most aggressive settings possible */
-//     0x78, 0xc0fff8c4, (1<<29)|(1<<28)|(1<<27)|(2<<24)|(2<<9)|DRT_CL|(1<<3)|(1<<1)|(1<<0),
-//     0x78, 0xc0f8f8c0, (1<<29)|(1<<28)|(1<<27)|(1<<24)|(1<<16)|(2<<9)|DRT_CL|(1<<3)|(3<<1)|(1<<0),
-       0x78, 0xc0f8f9c0, (1<<29)|(1<<28)|(1<<27)|(1<<24)|(1<<16)|(2<<9)|DRT_CL|(1<<3)|(3<<1)|(1<<0),
+//     0x78, 0xc0fff8c4, (1<<29)|(1<<28)|(1<<27)|(2<<24)|(2<<9)|CAS_LATENCY|(1<<3)|(1<<1)|(1<<0),
+//     0x78, 0xc0f8f8c0, (1<<29)|(1<<28)|(1<<27)|(1<<24)|(1<<16)|(2<<9)|CAS_LATENCY|(1<<3)|(3<<1)|(1<<0),
+//     0x78, 0xc0f8f9c0, (1<<29)|(1<<28)|(1<<27)|(1<<24)|(1<<16)|(2<<9)|CAS_LATENCY|(1<<3)|(3<<1)|(1<<0),
+
+       // The only things we need to set here are DRAM idle timer, Back-to-Back Read Turnaround, and
+       // Back-to-Back Write-Read Turnaround. All others are configured based on SPD.
+       0x78, 0xD7F8FFFF, (1<<29)|(1<<27)|(1<<16),
 
        /* FIXME why was I attempting to set a reserved bit? */
        /* 0x0100040f */
@@ -355,9 +281,12 @@ static const long register_values[] = {
         *         01 == Reserved
         *         10 == Error checking, using chip-kill, with correction
         *         11 == Reserved
-        * [19:18] Reserved
-        *         Must equal 01
-        * [17:17] (Intel Undocumented) should always be set to 1
+        * [19:18] DRB Granularity (Read-Only)
+        *         00 == 32 MB quantities (single channel mode)
+        *                 01 == 64 MB quantities (dual-channel mode)
+        *                 10 == Reserved
+        *                 11 == Reserved
+        * [17:17] (Intel Undocumented) should always be set to 1       (SJM: comment inconsistent with current setting, below)
         * [16:16] Command Per Clock - Address/Control Assertion Rule (CPC)
         *         0 == 2n Rule
         *         1 == 1n rule
@@ -370,7 +299,7 @@ static const long register_values[] = {
         *         111 == Refresh every 64 clocks (fast refresh)
         * [07:07] Reserved
         * [06:04] Mode Select (SMS)
-        *         000 == Self Refresh Mode
+        *         000 == Reserved (was Self Refresh Mode in E7500)
         *         001 == NOP Command
         *         010 == All Banks Precharge
         *         011 == Mode Register Set
@@ -383,15 +312,34 @@ static const long register_values[] = {
 //     .long 0x7c, 0xffcefcff, (1<<22)|(2 << 20)|(1 << 16)| (0 << 8),
 //     .long 0x7c, 0xff8cfcff, (1<<22)|(2 << 20)|(1 << 17)|(1 << 16)| (0 << 8),
 //     .long 0x7c, 0xff80fcff, (1<<22)|(2 << 20)|(1 << 18)|(1 << 17)|(1 << 16)| (0 << 8),
-       0x7c, 0xff82fcff, (1<<22)|(2 << 20)|(1 << 18)|(1 << 16)| (0 << 8),
-
 
-       /* Another Intel undocumented register */
-       0x88, 0x080007ff, (1<<31)|(1 << 30)|(1<<28)|(0 << 26)|(0x10 << 21)|(10 << 16)|(0x13 << 11),
+       // Default to dual-channel mode, ECC, 1-clock address/cmd hold 
+       // NOTE: configure_e7501_dram_controller_mode() configures further
+       0x7c, 0xff8ef8ff, (1<<22)|(2<<20)|(1<<16)|(0<<8),
+
+       /* Another Intel undocumented register
+        * 0x88 - 0x8B
+        * [31:31]      Purpose unknown
+        * [26:26]      Master DLL Reset?
+        *                      0 == Normal operation?
+        *                      1 == Reset?
+        * [07:07]      Periodic memory recalibration?
+        *                      0 == Disabled?
+        *                      1 == Enabled?
+        * [04:04]      Receive FIFO RE-Sync?
+        *                      0 == Normal operation?
+        *                      1 == Reset?
+        */
+        // NOTE: Some factory BIOSs don't do this.
+        //               Doesn't seem to matter either way.
+       0x88, 0xffffff00, 0x80,
 
        /* CLOCK_DIS - CK/CK# Disable Register
         * 0x8C
-        * [7:4] Reserved
+        * [7:7] DDR Frequency
+        *               0 == 100 MHz (200 MHz data rate)
+        *               1 == 133 MHz (266 MHz data rate)
+        * [6:4] Reserved
         * [3:3] CK3
         *       0 == Enable
         *       1 == Disable
@@ -405,6 +353,8 @@ static const long register_values[] = {
         *       0 == Enable
         *       1 == Disable
         */
+       // NOTE: Disable all clocks initially; turn ones we need back on
+       //               in enable_e7501_clocks()
        0x8C, 0xfffffff0, 0xf,
 
        /* TOLM - Top of Low Memory Register
@@ -420,12 +370,15 @@ static const long register_values[] = {
         * [09:00] Remap Base Address [35:26] 64M aligned
         *         Bits [25:0] are assumed to be 0.
         */
+
+       // NOTE: TOLM overridden by configure_e7501_ram_addresses()
        0xc4, 0xfc0007ff, (0x2000 << 0) | (0x3ff << 16),
+
        /* REMAPLIMIT - Remap Limit Address Register
         * 0xC8 - 0xC9
         * [15:10] Reserved
         * [09:00] Remap Limit Address [35:26] 64M aligned
-        * When remaplimit < remapbase this register is disabled.
+        * When remaplimit < remapbase the remap window is disabled.
         */
        0xc8, 0xfffffc00, 0,
 
@@ -446,1195 +399,1426 @@ static const long register_values[] = {
         *         0 == Present
         *         1 == Absent
         */
+
+       // Enable D0:D1, disable D2:F1, D3:F1, D4:F1
        0xe0, 0xffffffe2, (1<<4)|(1<<3)|(1<<2)|(0<<0),
-       0xd8, 0xffff9fff, 0x00000000,
-       0xf4, 0x3f8ffffd, 0x40300002,
-       0x1050, 0xffffffcf, 0x00000030, // d2f0
-};
 
+       // Undocumented
+       0xd8, 0xffff9fff, 0x00000000,
 
-       /*
-        * Routine:     ram_set_registers
-        * Arguments:   none
-        * Results:     none
-        * Trashed:     %eax, %ebx, %ecx, %edx, %esi, %eflags
-        * Effects:     Do basic ram setup that does not depend on serial
-        *              presence detect information.
-        *              This sets PCI configuration registers to known good
-        *              values based on the table: 
-        *                      constant_register_values
-        *              Which are a triple of configuration regiser, mask, and value.
-        *              
+       // Undocumented - this is pure conjecture based on similarity to 855PM
+       /* MCHTST - MCH Test Register
+        * 0xF4 - 0xF7
+        * [31:31] Purpose unknown
+        * [30:30] Purpose unknown
+        * [29:23] Unknown - not used?
+        * [22:22] System Memory MMR Enable
+        *         0 == Disable: mem space and BAR at 0x14 are not accessible
+        *         1 == Enable: mem space and BAR at 0x14 are accessible
+        * [21:20] Purpose unknown
+        * [19:02] Unknown - not used?
+        * [01:01] D6EN (Device #6 enable)
+        *         0 == Disable
+        *         1 == Enable
+        * [00:00] Unknown - not used?
         */
-/* from 1M or 512K */
-#define RCOMP_MMIO 0x100000
 
-       /* DDR RECOMP table */
+       0xf4, 0x3f8ffffd, 0x40300002,
+
+#ifdef SUSPICIOUS_LOOKING_CODE
+       // SJM: Undocumented. 
+       //              This will access D2:F0:0x50, is this correct??
+       0x1050, 0xffffffcf, 0x00000030,
+#endif
+};
+
+       /* DDR RECOMP tables */
 
-static const long ddr_rcomp_1[] = {
+// Slew table for 1x drive?
+static const uint32_t maybe_1x_slew_table[] = {
        0x44332211, 0xc9776655, 0xffffffff, 0xffffffff,
        0x22111111, 0x55444332, 0xfffca876, 0xffffffff,
 };
-static const long ddr_rcomp_2[] = {
+
+// Slew table for 2x drive?
+static const uint32_t maybe_2x_slew_table[] = {
        0x00000000, 0x76543210, 0xffffeca8, 0xffffffff,
        0x21000000, 0xa8765432, 0xffffffec, 0xffffffff,
 };
-static const long ddr_rcomp_3[] = {
+
+// Pull Up / Pull Down offset table, if analogous to IXP2800?
+static const uint32_t maybe_pull_updown_offset_table[] = {
        0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff,
        0x88888888, 0x88888888, 0x88888888, 0x88888888,
 };
 
-#define rcomp_init_str "Setting RCOMP registers.\r\n"
-
-static void write_8dwords(uint32_t src_addr, uint32_t dst_addr) {
-       int i;
-       uint32_t dword;
-       for(i=0;i<8;i++) {
-               dword = read32(src_addr);
-               write32(dst_addr, dword);
-               src_addr+=4;
-               dst_addr+=4;
-               
-       }
-}
-
-#if 1
+/*^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^*/
+/*                                                                             TABLES                                                                    */
+/**********************************************************************************/
 #define SLOW_DOWN_IO inb(0x80);
-#else
-#define SLOW_DOWN_IO udelay(40);
-#endif
+//#define SLOW_DOWN_IO udelay(40);
 
-        /* Estimate that SLOW_DOWN_IO takes about 50&76us*/
-        /* delay for 200us */
+       /* Estimate that SLOW_DOWN_IO takes about 50&76us*/
+       /* delay for 200us */
 
 #if 1
 static void do_delay(void)
 {
-        int i;
-        for(i = 0; i < 16; i++) { SLOW_DOWN_IO }
+       int i;
+       for(i = 0; i < 16; i++) { SLOW_DOWN_IO }
 }
 #define DO_DELAY do_delay();
 #else
 #define DO_DELAY \
-        udelay(200);
-#endif
+       udelay(200);
+#endif         
 
 #define EXTRA_DELAY DO_DELAY
 
-static void ram_set_rcomp_regs(const struct mem_controller *ctrl) {
-       uint32_t dword;
-#if DEBUG_RAM_CONFIG
-       print_debug(rcomp_init_str);
-#endif
-
-       /*enable access to the rcomp bar */
-       dword = pci_read_config32(ctrl->d0, 0x0f4);
-        dword &= ~(1<<31);
-        dword |=((1<<30)|1<<22);
-        pci_write_config32(ctrl->d0, 0x0f4, dword);
-        
-
-       /* Set the MMIO address to 512K */
-        pci_write_config32(ctrl->d0, 0x14, RCOMP_MMIO);
-
-       dword = read32(RCOMP_MMIO + 0x20);
-       dword |= (1<<9);
-       write32(RCOMP_MMIO + 0x20, dword);
-       
-
-       /* Begin to write the RCOMP registers */
-       
-       write8(RCOMP_MMIO + 0x2c, 0xff);
-       write32(RCOMP_MMIO + 0x30, 0x01040444);
-       write8(RCOMP_MMIO + 0x34, 0x04);
-       write32(RCOMP_MMIO + 0x40, 0);
-       write16(RCOMP_MMIO + 0x44, 0);
-       write16(RCOMP_MMIO + 0x48, 0);
-       write16(RCOMP_MMIO + 0x50, 0);
-       write_8dwords((uint32_t)ddr_rcomp_1, RCOMP_MMIO + 0x60);
-       write_8dwords((uint32_t)ddr_rcomp_2, RCOMP_MMIO + 0x80);
-       write_8dwords((uint32_t)ddr_rcomp_2, RCOMP_MMIO + 0xa0);
-       write_8dwords((uint32_t)ddr_rcomp_2, RCOMP_MMIO + 0x140);
-       write_8dwords((uint32_t)ddr_rcomp_2, RCOMP_MMIO + 0x1c0);
-       write_8dwords((uint32_t)ddr_rcomp_3, RCOMP_MMIO + 0x180);
-
-       dword = read32(RCOMP_MMIO + 0x20);
-       dword &= ~(3);
-       dword |= 1;
-       write32(RCOMP_MMIO + 0x20, dword);
-
-       /* Wait 40 usec */
-       SLOW_DOWN_IO;
-       
-       /* unblock updates */
-       dword = read32(RCOMP_MMIO + 0x20);
-       dword &= ~(1<<9);
-       write32(RCOMP_MMIO+0x20, dword);
-       dword |= (1<<8);
-       write32(RCOMP_MMIO+0x20, dword);
-       dword &= ~(1<<8);
-       write32(RCOMP_MMIO+0x20, dword);
-       
-       /* Wait 40 usec */
-       SLOW_DOWN_IO;
-
-       /*disable access to the rcomp bar */
-       dword = pci_read_config32(ctrl->d0, 0x0f4);
-       dword &= ~(1<<22);
-       pci_write_config32(ctrl->d0, 0x0f4, dword);     
-
-}
-
-static void ram_set_d0f0_regs(const struct mem_controller *ctrl) {
-#if DEBUG_RAM_CONFIG
-       dumpnorth();
-#endif
-       int i;
-       int max;
-        max = sizeof(register_values)/sizeof(register_values[0]);
-        for(i = 0; i < max; i += 3) {
-                uint32_t reg;
-#if DEBUG_RAM_CONFIG
-                print_debug_hex32(register_values[i]);
-                print_debug(" <-");
-                print_debug_hex32(register_values[i+2]);
-                print_debug("\r\n");
-#endif
-                reg = pci_read_config32(ctrl->d0,register_values[i]);
-                reg &= register_values[i+1];
-                reg |= register_values[i+2] & ~(register_values[i+1]);
-                pci_write_config32(ctrl->d0,register_values[i], reg);
 
+/*^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^*/
+/*                                                                     DELAY FUNCTIONS                                                           */
+/**********************************************************************************/
 
-        }
-#if DEBUG_RAM_CONFIG
-       dumpnorth();
-#endif
-}
-static void sdram_set_registers(const struct mem_controller *ctrl){
-        ram_set_rcomp_regs(ctrl);
-        ram_set_d0f0_regs(ctrl);
+static void die_on_spd_error(int spd_return_value)
+{
+       if (spd_return_value < 0)
+               die("Error reading SPD info\r\n");
 }
 
-
-       /*
-        * Routine:     sdram_spd_get_page_size
-        * Arguments:   %bl SMBUS_MEM_DEVICE
-        * Results:     
-        *              %edi log base 2 page size of DIMM side 1 in bits
-        *              %esi log base 2 page size of DIMM side 2 in bits
-        *
-        * Preserved:   %ebx (except %bh), %ebp
-        *
-        * Trashed:     %eax, %bh, %ecx, %edx, %esp, %eflags
-        * Used:        %eax, %ebx, %ecx, %edx, %esi, %edi, %esp, %eflags
-        *
-        * Effects:     Uses serial presence detect to set %edi & %esi
-        *              to the page size of a dimm.
-        * Notes:
-        *              %bl SMBUS_MEM_DEVICE
-        *              %edi holds the page size for the first side of the DIMM.
-        *              %esi holds the page size for the second side of the DIMM.
-        *                   memory size is represent as a power of 2.
-        *
-        *              This routine may be worth moving into generic code somewhere.
-        */
-struct dimm_page_size { 
-        unsigned long side1;
-        unsigned long side2;
-};      
-  
-static struct dimm_page_size sdram_spd_get_page_size(unsigned device) {
-
-       uint32_t ecx;
+//----------------------------------------------------------------------------------
+// Function:           sdram_spd_get_page_size
+// Parameters:         dimm_socket_address - SMBus address of DIMM socket to interrogate
+// Return Value:       struct dimm_size - log2(page size) for each side of the DIMM.
+// Description:        Calculate the page size for each physical bank of the DIMM:
+//                                             log2(page size) = (# columns) + log2(data width)
+//
+//                                     NOTE: page size is the total number of data bits in a row.
+//
+static struct dimm_size sdram_spd_get_page_size(uint16_t dimm_socket_address) 
+{
+       uint16_t module_data_width;
        int value;
-       struct dimm_page_size pgsz;
+       struct dimm_size pgsz;
 
        pgsz.side1 = 0;
        pgsz.side2 = 0; 
                
-       value  = spd_read_byte(device, 4); /* columns */
-       if(value < 0) goto hw_err;
-       pgsz.side1 = value & 0xf;
+       // Side 1
+       value  = spd_read_byte(dimm_socket_address, SPD_NUM_COLUMNS);
+       if (value < 0) goto hw_err;
+       pgsz.side1 = value & 0xf;                       // # columns in bank 1
        
        /* Get the module data width and convert it to a power of two */
-       value = spd_read_byte(device,7);                /* (high byte) */
-       if(value < 0) goto hw_err;
-       ecx = value & 0xff;
-       ecx <<= 8;
+       value = spd_read_byte(dimm_socket_address, SPD_MODULE_DATA_WIDTH_MSB);
+       if (value < 0) goto hw_err;
+       module_data_width = (value & 0xff) << 8;
 
-       value = spd_read_byte(device, 6);        /* (low byte) */
-       if(value < 0) goto hw_err;
-       ecx |= (value & 0xff);
+       value = spd_read_byte(dimm_socket_address, SPD_MODULE_DATA_WIDTH_LSB);
+       if (value < 0) goto hw_err;
+       module_data_width |= (value & 0xff);
 
-       pgsz.side1 += log2(ecx);         /* compute cheap log base 2 */ 
+       pgsz.side1 += log2(module_data_width);
 
        /* side two */
-       value = spd_read_byte(device, 5);       /* number of physical banks */
-       if(value < 0) goto hw_err;
-       if(value==1) goto out;
-       if(value!=2) goto val_err;
-
-       /* Start with the symmetrical case */
-       pgsz.side2 = pgsz.side1;
-       value = spd_read_byte(device,4);   /* columns */
-       if(value < 0) goto hw_err;
-       if((value & 0xf0)==0 ) goto out;
-       pgsz.side2 -=value & 0xf; /* Subtract out columns on side 1 */
-       pgsz.side2 +=(value>>4)& 0xf; /* Add in columns on side 2 */
-        goto out;
-
- val_err:
-        die("Bad SPD value\r\n");
-        /* If an hw_error occurs report that I have no memory */
-hw_err:
-       pgsz.side1 = 0;
-       pgsz.side2 = 0;
-out:
+       value = spd_read_byte(dimm_socket_address, SPD_NUM_DIMM_BANKS);
+       if (value < 0) goto hw_err;
+       if (value > 2) 
+               die("Bad SPD value\r\n");
+       if (value == 2) {
+
+               pgsz.side2 = pgsz.side1;                // Assume symmetric banks until we know differently
+               value = spd_read_byte(dimm_socket_address, SPD_NUM_COLUMNS);
+               if (value < 0) goto hw_err;
+               if ((value & 0xf0) != 0) {
+                       // Asymmetric banks
+                       pgsz.side2 -= value & 0xf;              /* Subtract out columns on side 1 */
+                       pgsz.side2 += (value>>4) & 0xf; /* Add in columns on side 2 */
+               }
+       }
+
        return pgsz;    
+
+hw_err:
+       die(SPD_ERROR);
+       return pgsz;    // Never reached
 }
 
 
-       /*
-        * Routine:     sdram_spd_get_width
-        * Arguments:   %bl SMBUS_MEM_DEVICE
-        * Results:     
-        *              %edi width of SDRAM chips on DIMM side 1 in bits
-        *              %esi width of SDRAM chips on DIMM side 2 in bits
-        *
-        * Preserved:   %ebx (except %bh), %ebp
-        *
-        * Trashed:     %eax, %bh, %ecx, %edx, %esp, %eflags
-        * Used:        %eax, %ebx, %ecx, %edx, %esi, %edi, %esp, %eflags
-        *
-        * Effects:     Uses serial presence detect to set %edi & %esi
-        *              to the width of a dimm.
-        * Notes:
-        *              %bl SMBUS_MEM_DEVICE
-        *              %edi holds the width for the first side of the DIMM.
-        *              %esi holds the width for the second side of the DIMM.
-        *                   memory size is represent as a power of 2.
-        *
-        *              This routine may be worth moving into generic code somewhere.
-        */
-struct dimm_width {
-        unsigned side1;
-        unsigned side2;
-};      
-  
-static struct dimm_width sdram_spd_get_width(unsigned device) {
+//----------------------------------------------------------------------------------
+// Function:           sdram_spd_get_width
+// Parameters:         dimm_socket_address - SMBus address of DIMM socket to interrogate
+// Return Value:       dimm_size - width in bits of each DIMM side's DRAMs.
+// Description:        Read the width in bits of each DIMM side's DRAMs via SPD.
+//                                     (i.e. 4, 8, 16)
+//
+static struct dimm_size sdram_spd_get_width(uint16_t dimm_socket_address) 
+{
        int value;
-       struct dimm_width wd;
-       uint32_t ecx;
+       struct dimm_size width;
        
-       wd.side1 = 0;
-       wd.side2 = 0;
+       width.side1 = 0;
+       width.side2 = 0;
 
-       value = spd_read_byte(device, 13); /* sdram width */
-       if(value < 0 )  goto hw_err;
-       ecx = value;
+       value = spd_read_byte(dimm_socket_address, SPD_PRIMARY_DRAM_WIDTH);
+       die_on_spd_error(value);
        
-       wd.side1 = value & 0x7f;        
-       
-       /* side two */
-       value = spd_read_byte(device, 5); /* number of physical banks */
-       if(value < 0 ) goto hw_err;     
-       if(value <=1 ) goto out;
-
-       /* Start with the symmetrical case */
-       wd.side2 = wd.side1;
+       width.side1 = value & 0x7f;                     // Mask off bank 2 flag
+
+       if (value & 0x80) {
+               width.side2 = width.side1 << 1; // Bank 2 exists and is double-width
+       } else {
+               // If bank 2 exists, it's the same width as bank 1
+               value = spd_read_byte(dimm_socket_address, SPD_NUM_DIMM_BANKS);
+               die_on_spd_error(value);        
+
+#ifdef ROMCC_IF_BUG_FIXED
+               if (value == 2)
+                       width.side2 = width.side1;
+#else
+               switch (value) {
+               case 2:
+                       width.side2 = width.side1;
+                       break;
 
-       if((ecx & 0x80)==0) goto out;
-       
-       wd.side2 <<=1;
-hw_err:
-       wd.side1 = 0;
-       wd.side2 = 0;
+               default:
+                       break;
+               }
+#endif
+       }
 
- out:
-        return wd;
+       return width;
 }
        
-       /*
-        * Routine:     sdram_spd_get_dimm_size
-        * Arguments:   %bl SMBUS_MEM_DEVICE
-        * Results:     
-        *              %edi log base 2 size of DIMM side 1 in bits
-        *              %esi log base 2 size of DIMM side 2 in bits
-        *
-        * Preserved:   %ebx (except %bh), %ebp
-        *
-        * Trashed:     %eax, %bh, %ecx, %edx, %esp, %eflags
-        * Used:        %eax, %ebx, %ecx, %edx, %esi, %edi, %esp, %eflags
-        *
-        * Effects:     Uses serial presence detect to set %edi & %esi
-        *              the size of a dimm.
-        * Notes:
-        *              %bl SMBUS_MEM_DEVICE
-        *              %edi holds the memory size for the first side of the DIMM.
-        *              %esi holds the memory size for the second side of the DIMM.
-        *                   memory size is represent as a power of 2.
-        *
-        *              This routine may be worth moving into generic code somewhere.
-        */
+//----------------------------------------------------------------------------------
+// Function:           spd_get_dimm_size
+// Parameters:         dimm_socket_address - SMBus address of DIMM socket to interrogate
+// Return Value:       dimm_size - log2(number of bits) for each side of the DIMM
+// Description:        Calculate the log base 2 size in bits of both DIMM sides.
+//                                             log2(# bits) = (# columns) + log2(data width) + 
+//                                                                        (# rows) + log2(banks per SDRAM)
+//
+//                                     Note that it might be easier to use SPD byte 31 here, it has the 
+//                                     DIMM size as a multiple of 4MB.  The way we do it now we can size 
+//                                     both sides of an asymmetric dimm.
+//
+static struct dimm_size spd_get_dimm_size(unsigned dimm_socket_address)
+{
+   int value;
 
-struct dimm_size {
-        unsigned long side1;
-        unsigned long side2;
-};
+       // Start with log2(page size)
+    struct dimm_size sz = sdram_spd_get_page_size(dimm_socket_address);
 
-static struct dimm_size spd_get_dimm_size(unsigned device)
-{
-        /* Calculate the log base 2 size of a DIMM in bits */
-        struct dimm_size sz;
-        int value, low;
-        sz.side1 = 0;
-        sz.side2 = 0;
-
-        /* Note it might be easier to use byte 31 here, it has the DIMM size as
-         * a multiple of 4MB.  The way we do it now we can size both
-         * sides of an assymetric dimm.
-         */
-        value = spd_read_byte(device, 3);       /* rows */
-        if (value < 0) goto hw_err;
-//        if ((value & 0xf) == 0) goto val_err;
-        sz.side1 += value & 0xf;
+       if (sz.side1 > 0) {
+
+               value = spd_read_byte(dimm_socket_address, SPD_NUM_ROWS);
+               die_on_spd_error(value);
 
-        value = spd_read_byte(device, 4);       /* columns */
-        if (value < 0) goto hw_err;
-//        if ((value & 0xf) == 0) goto val_err;
         sz.side1 += value & 0xf;
 
-        value = spd_read_byte(device, 17);      /* banks */
-        if (value < 0) goto hw_err;
-//        if ((value & 0xff) == 0) goto val_err;
-       value &=0xff;
-        sz.side1 += log2(value);
+               if (sz.side2 > 0) {
 
-        /* Get the module data width and convert it to a power of two */
-        value = spd_read_byte(device, 7);       /* (high byte) */
-        if (value < 0) goto hw_err;
-        value &= 0xff;
-        value <<= 8;
-        
-        low = spd_read_byte(device, 6); /* (low byte) */
-        if (low < 0) goto hw_err;
-        value |= (low & 0xff);
-//        if ((value != 72) && (value != 64)) goto val_err;
-        sz.side1 += log2(value);
-        
-        /* side 2 */
-        value = spd_read_byte(device, 5);       /* number of physical banks */
-        if (value < 0) goto hw_err;
-        if (value == 1) goto out;
-//        if (value != 2) goto val_err;
+                       // Double-sided DIMM
+                       if (value & 0xF0)
+                               sz.side2 += value >> 4;         // Asymmetric
+                       else
+                               sz.side2 += value;                      // Symmetric
+               }
 
-        /* Start with the symmetrical case */
-        sz.side2 = sz.side1;
+        value = spd_read_byte(dimm_socket_address, SPD_NUM_BANKS_PER_DRAM);
+        die_on_spd_error(value);
 
-        value = spd_read_byte(device, 3);       /* rows */
-        if (value < 0) goto hw_err;
-        if ((value & 0xf0) == 0) goto out;      /* If symmetrical we are done */
-        sz.side2 -= (value & 0x0f);             /* Subtract out rows on side 1 */
-        sz.side2 += ((value >> 4) & 0x0f);      /* Add in rows on side 2 */
+               value = log2(value);
+        sz.side1 += value;
+               if (sz.side2 > 0)
+               sz.side2 += value;
+       }
 
-        value = spd_read_byte(device, 4);       /* columns */
-        if (value < 0) goto hw_err;
-//        if ((value & 0xff) == 0) goto val_err;
-        sz.side2 -= (value & 0x0f);             /* Subtract out columns on side 1 */
-        sz.side2 += ((value >> 4) & 0x0f);      /* Add in columsn on side 2 */
-        goto out;
-
- val_err:
-        die("Bad SPD value\r\n");
-        /* If an hw_error occurs report that I have no memory */
-hw_err:
-        sz.side1 = 0;
-        sz.side2 = 0;
- out:
-        return sz;
+       return sz;
 }
 
+//----------------------------------------------------------------------------------
+// Function:           are_spd_values_equal
+// Parameters:         spd_byte_number - 
+//                                     dimmN_address - SMBus addresses of DIMM sockets to interrogate
+// Return Value:       1 if both DIMM sockets report the same value for the specified
+//                                             SPD parameter; 0 if the values differed or an error occurred.
+// Description:        Determine whether two DIMMs have the same value for a SPD parameter.
+//
+static uint8_t are_spd_values_equal(uint8_t spd_byte_number, uint16_t dimm0_address,
+                                                                       uint16_t dimm1_address)
+{
+       uint8_t bEqual = 0;
 
+       int dimm0_value = spd_read_byte(dimm0_address, spd_byte_number);
+       int dimm1_value = spd_read_byte(dimm1_address, spd_byte_number);
 
-       /*
-        * This is a place holder fill this out
-        * Routine:     spd_set_row_attributes 
-        * Arguments:   %bl SMBUS_MEM_DEVICE
-        * Results:     
-        *              %edi log base 2 size of DIMM side 1 in bits
-        *              %esi log base 2 size of DIMM side 2 in bits
-        *
-        * Preserved:   %ebx (except %bh), %ebp
-        *
-        * Trashed:     %eax, %bh, %ecx, %edx, %esp, %eflags
-        * Used:        %eax, %ebx, %ecx, %edx, %esi, %edi, %esp, %eflags
-        *
-        * Effects:     Uses serial presence detect to set %edi & %esi
-        *              the size of a dimm.
-        * Notes:
-        *              %bl SMBUS_MEM_DEVICE
-        *              %edi holds the memory size for the first side of the DIMM.
-        *              %esi holds the memory size for the second side of the DIMM.
-        *                   memory size is represent as a power of 2.
-        *
-        *              This routine may be worth moving into generic code somewhere.
-        */
-static long spd_set_row_attributes(const struct mem_controller *ctrl, long dimm_mask) {
-       int i;  
-        uint32_t dword=0;
-        int value;
-        
-
-        /* Walk through all dimms and find the interesection of the support
-         * for ecc sdram and refresh rates
-         */        
-        
-        for(i = 0; i < DIMM_SOCKETS; i++) {
-               if (!(dimm_mask & (1 << i))) {
-                        continue;
-                }
-                 /* Test to see if I have ecc sdram */
-               struct dimm_page_size sz;
-                sz = sdram_spd_get_page_size(ctrl->channel0[i]);  /* SDRAM type */
-#if DEBUG_RAM_CONFIG
-               print_debug("page size =");
-               print_debug_hex32(sz.side1);
-               print_debug(" ");
-               print_debug_hex32(sz.side2);
-               print_debug("\r\n");
-#endif
-       
-               /* Test to see if the dimm is present */
-               if( sz.side1 !=0) {
-
-                       /* Test for a valid dimm width */
-                       if((sz.side1 <15) || (sz.side1>18) ) {
-                               print_err("unsupported page size\r\n");
-                       }
+       if ((dimm0_value >= 0) && (dimm1_value >= 0) && (dimm0_value == dimm1_value))
+               bEqual = 1;
 
-                       /* double because I have 2 channels */
-                       sz.side1++;
+       return bEqual;
+}
 
-                       /* Convert to the format needed for the DRA register */
-                       sz.side1-=14;   
+//----------------------------------------------------------------------------------
+// Function:           spd_get_supported_dimms
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+// Return Value:       uint8_t - a bitmask indicating which of the possible sockets
+//                                             for each channel was found to contain a compatible DIMM.
+//                                             Bit 0 corresponds to the closest socket for channel 0,
+//                                             Bit 1 to the next socket for channel 0,
+//                                             ...
+//                                             Bit MAX_DIMM_SOCKETS_PER_CHANNEL-1 to the last socket for channel 0,
+//                                             Bit MAX_DIMM_SOCKETS_PER_CHANNEL is the closest socket for channel 1,
+//                                             ...
+//                                             Bit 2*MAX_DIMM_SOCKETS_PER_CHANNEL-1 is the last socket for channel 1
+// Description:        Scan for compatible DIMMs.
+//                                     The code in this module only supports dual-channel operation,
+//                                     so we test that compatible DIMMs are paired.
+//
+static uint8_t spd_get_supported_dimms(const struct mem_controller *ctrl) 
+{
+       int i;
+       uint8_t dimm_mask = 0;
 
-                       /* Place in the %ebp the dra place holder */ //i
-                       dword |= sz.side1<<(i<<3);
-                       
-                       /* Test to see if the second side is present */
+       // Have to increase size of dimm_mask if this assertion is violated
+       ASSERT(MAX_DIMM_SOCKETS_PER_CHANNEL <= 4);
 
-                       if( sz.side2 !=0) {
-        
-                               /* Test for a valid dimm width */
-                               if((sz.side2 <15) || (sz.side2>18) ) {
-                                       print_err("unsupported page size\r\n");
-                               }
+       // Find DIMMs we can support on channel 0.
+       // Then see if the corresponding channel 1 DIMM has the same parameters,
+       // since we only support dual-channel.
 
-                               /* double because I have 2 channels */
-                               sz.side2++;
+    for (i = 0; i < MAX_DIMM_SOCKETS_PER_CHANNEL; i++) {
 
-                               /* Convert to the format needed for the DRA register */
-                               sz.side2-=14;
+        uint16_t channel0_dimm = ctrl->channel0[i];
+               uint16_t channel1_dimm = ctrl->channel1[i];
+               uint8_t bDualChannel = 1;
+               struct dimm_size        page_size;
+               struct dimm_size        sdram_width;
+               int spd_value;
+               int j;
 
-                               /* Place in the %ebp the dra place holder */ //i
-                               dword |= sz.side2<<((i<<3) + 4 );
+               if (channel0_dimm == 0)
+                       continue;               // No such socket on this mainboard
 
-                       }
-               }
+        if (spd_read_byte(channel0_dimm, SPD_MEMORY_TYPE) != MEMORY_TYPE_SDRAM_DDR)
+                       continue;
 
-               /* Now add the SDRAM chip width to the DRA */
-               struct dimm_width wd;
-               wd = sdram_spd_get_width(ctrl->channel0[i]);
+#ifdef VALIDATE_DIMM_COMPATIBILITY
+               if (spd_read_byte(channel0_dimm, SPD_MODULE_VOLTAGE) != SPD_VOLTAGE_SSTL2)
+                       continue;               // Unsupported voltage
 
-#if DEBUG_RAM_CONFIG
-                print_debug("width =");
-                print_debug_hex32(wd.side1);
-                print_debug(" ");
-                print_debug_hex32(wd.side2);
-                print_debug("\r\n");
-#endif
+               // E7501 does not support unregistered DIMMs
+               spd_value = spd_read_byte(channel0_dimm, SPD_MODULE_ATTRIBUTES);
+               if (!(spd_value & MODULE_REGISTERED) || (spd_value < 0))
+                       continue;
                
-               if(wd.side1 == 0) continue;
-               if(wd.side1 == 4) {
-                       /* Enable an x4 device */
-                       dword |= 0x08 << (i<<3);
+        // Must support burst = 4 for dual-channel operation on E7501
+               // NOTE: for single-channel, burst = 8 is required
+               spd_value = spd_read_byte(channel0_dimm, SPD_SUPPORTED_BURST_LENGTHS);
+               if (!(spd_value & SPD_BURST_LENGTH_4) || (spd_value < 0))
+                       continue;
+
+        page_size      = sdram_spd_get_page_size(channel0_dimm);
+               sdram_width = sdram_spd_get_width(channel0_dimm);
+
+               // Validate DIMM page size
+               // The E7501 only supports page sizes of 4, 8, 16, or 32 KB per channel
+               // NOTE: 4 KB =  32 Kb = 2^15
+               //              32 KB = 262 Kb = 2^18
+
+               if ((page_size.side1 < 15) || (page_size.side1 > 18))
+                       continue;
+
+               // If DIMM is double-sided, verify side2 page size
+        if (page_size.side2 != 0) {
+                   if ((page_size.side2 < 15) || (page_size.side2 > 18))
+                               continue;
                }
 
-               if(wd.side2 == 0) continue;
-                if(wd.side2 == 4) {
-                        /* Enable an x4 device */
-                        dword |= 0x08 << ((i<<3 ) + 4);
-                }
-               
-       /* go to the next DIMM */
-       }
-
-       /* Write the new row attributes register */
-       pci_write_config32(ctrl->d0, 0x70, dword);
-
-       return dimm_mask;
-
-}
-
-#define spd_pre_init  "Reading SPD data...\r\n"
-#define spd_pre_set "setting based on SPD data...\r\n"
-#define spd_post_init "done\r\n"
+               // Validate SDRAM width
+               // The E7501 only supports x4 and x8 devices
 
+               if ((sdram_width.side1 != 4) && (sdram_width.side1 != 8))
+                       continue;
 
-static const uint32_t refresh_rate_rank[]= {
-       /* Refresh rates ordered from most conservative (lowest)
-        * to most agressive (highest)
-        * disabled 0 -> rank 3 
-        * 15.6usec 1 -> rank 1
-        * 7.8 usec 2 -> rank 0
-        * 64usec   3 -> rank 2
-        */
-       3, 1, 0, 2 };
-static const uint32_t refresh_rate_index[] = {
-       /* Map the spd refresh rates to memory controller settings 
-        * 15.625us -> 15.6us
-        * 3.9us    -> err
-        * 7.8us    -> 7.8us
-        * 31.3s    -> 15.6us
-        * 62.5us   -> 15.6us
-        * 125us    -> 64us
-        */
-       1, 0xff, 2, 1, 1, 3
-};
-#define MAX_SPD_REFRESH_RATE 5
+               // If DIMM is double-sided, verify side2 width
+        if (sdram_width.side2 != 0) {
+                       if ((sdram_width.side2 != 4) && (sdram_width.side2 != 8))
+                               continue;
+               }
+#endif 
+               // Channel 0 DIMM looks compatible.
+               // Now see if it is paired with the proper DIMM on channel 1.
 
-static long spd_set_dram_controller_mode (const struct mem_controller *ctrl, long dimm_mask) {
+               ASSERT(channel1_dimm != 0);             // No such socket on this mainboard??
 
-        int i;  
-        uint32_t dword;
-        int value;
-       uint32_t ecx;
-       uint32_t edx;
-        
-        /* Read the inititial state */
-        dword = pci_read_config32(ctrl->d0, 0x7c);
-
-#if 0
-        /* Test if ECC cmos option is enabled */
-        movb    $RTC_BOOT_BYTE, %al
-        outb    %al, $0x70
-        inb     $0x71, %al
-        testb   $(1<<2), %al
-        jnz     1f
-        /* Clear the ecc enable */
-        andl    $~(3 << 20), %esi
-1:
-#endif
+               // NOTE: unpopulated DIMMs cause read to fail
+               spd_value = spd_read_byte(channel1_dimm, SPD_MODULE_ATTRIBUTES);
+               if (!(spd_value & MODULE_REGISTERED) || (spd_value < 0)) {
+                       
+                       print_debug("Skipping un-matched DIMMs - only dual-channel operation supported\r\n");
+                       continue;
+               }
 
+#ifdef VALIDATE_DIMM_COMPATIBILITY
+               spd_value = spd_read_byte(channel1_dimm, SPD_SUPPORTED_BURST_LENGTHS);
+               if (!(spd_value & SPD_BURST_LENGTH_4) || (spd_value < 0))
+                       continue;
 
-        /* Walk through all dimms and find the interesection of the support
-         * for ecc sdram and refresh rates
-         */        
+               for (j=0; j<sizeof(dual_channel_parameters); ++j) {
+                       if (!are_spd_values_equal(dual_channel_parameters[j], channel0_dimm, channel1_dimm)) {
 
-        for(i = 0; i < DIMM_SOCKETS; i++) {
-               if (!(dimm_mask & (1 << i))) {
-                        continue;
-                }
-                /* Test to see if I have ecc sdram */
-                value = spd_read_byte(ctrl->channel0[i], 11);  /* SDRAM type */
-                if(value < 0) continue;
-               if(value !=2 ) {
-                       /* Clear the ecc enable */
-                       dword &= ~(3 << 20);
+                               bDualChannel = 0;
+                               break;
+                       }
                }
-               value = spd_read_byte(ctrl->channel0[i], 12);  /* SDRAM refresh rate */
-               if(value < 0 ) continue;
-               value &= 0x7f;
-               if(value > MAX_SPD_REFRESH_RATE) { print_err("unsupported refresh rate\r\n");}
-//             if(value == 0xff) { print_err("unsupported refresh rate\r\n");}
-               
-               ecx = refresh_rate_index[value];
+#endif
 
-               /* Isolate the old refresh rate setting */
-               /* Load the refresh rate ranks */
-               edx = refresh_rate_rank[(dword >> 8) & 3]<<8;
-               edx |= refresh_rate_rank[ecx] & 0xff; 
-       
-               /* See if the new refresh rate is more conservative than the old
-               * refresh rate setting. (Lower ranks are more conservative)
-               */
-               if((edx & 0xff)< ((edx >> 8) & 0xff) ) {
-                       /* Clear the old refresh rate */
-                       dword &= ~(3<<8);
-                       /* Move in the new refresh rate */
-                       dword |= (ecx<<8);
+               // Code around ROMCC bug in optimization of "if" statements
+#ifdef ROMCC_IF_BUG_FIXED
+               if (bDualChannel) {
+                       // Made it through all the checks, this DIMM pair is usable
+                       dimm_mask |= ((1<<i) | (1<<(MAX_DIMM_SOCKETS_PER_CHANNEL + i)));
                }
+               else
+                       print_debug("Skipping un-matched DIMMs - only dual-channel operation supported\r\n");
+#else
+               switch (bDualChannel) {
+               case 0:
+                       print_debug("Skipping un-matched DIMMs - only dual-channel operation supported\r\n");
+                       break;
                
-               value = spd_read_byte(ctrl->channel0[i], 33); /* Address and command hold time after clock */
-               if(value < 0) continue;
-               if(value >= 0xa0) {             /* At 133Mhz this constant should be 0x75 */
-                       dword &= ~(1<<16);      /* Use two clock cyles instead of one */
+               default:
+                       // Made it through all the checks, this DIMM pair is usable
+                       dimm_mask |= (1<<i) | (1<<(MAX_DIMM_SOCKETS_PER_CHANNEL + i));
+                       break;
                }
-       
-       /* go to the next DIMM */
+#endif         
        }
 
-       /* Now write the controller mode */
-       pci_write_config32(ctrl->d0, 0x7c, dword);
-       
        return dimm_mask;
-
 }
-static long spd_enable_clocks(const struct mem_controller *ctrl, long dimm_mask)
+
+/*^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^*/
+/*                                             SPD (SERIAL PRESENCE DETECT) FUNCTIONS                                    */
+/**********************************************************************************/
+
+//----------------------------------------------------------------------------------
+// Function:           do_ram_command
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+//                                     command - specifies the command to be sent to the DIMMs:
+//                                             RAM_COMMAND_NOP                 - No Operation
+//                                             RAM_COMMAND_PRECHARGE   - Precharge all banks
+//                                             RAM_COMMAND_MRS                 - Load Mode Register
+//                                             RAM_COMMAND_EMRS                - Load Extended Mode Register
+//                                             RAM_COMMAND_CBR                 - Auto Refresh ("CAS-before-RAS")
+//                                             RAM_COMMAND_NORMAL              - Normal operation
+//                                     jedec_mode_bits - for mode register set & extended mode register set
+//                                             commands, bits 0-12 contain the register value in JEDEC format.
+// Return Value:       None
+// Description:        Send the specified command to all DIMMs.
+//
+static void do_ram_command(const struct mem_controller *ctrl, uint8_t command, 
+                                                  uint16_t jedec_mode_bits) 
 {
-        int i;
-       uint32_t dword;
-       int value;
+    int i;
+       uint32_t dram_controller_mode;
+       uint8_t dimm_start_64M_multiple = 0;
+       uint16_t e7501_mode_bits = jedec_mode_bits;
 
-        /* Read the inititial state */
-        dword = pci_read_config32(ctrl->d0, 0x8c);
-/*
-# Intel clears top bit here, should we?
-# No the default is on and for normal timming it should be on.  Tom Z
-        andl    $0x7f, %esi
-*/
+       // Configure the RAM command
+    dram_controller_mode = pci_read_config32(ctrl->d0, DRC);
+    dram_controller_mode &= 0xFFFFFF8F;
+    dram_controller_mode |= command;
+    pci_write_config32(ctrl->d0, DRC, dram_controller_mode);
 
-        for(i = 0; i < DIMM_SOCKETS; i++) {
-               if (!(dimm_mask & (1 << i))) {
-                        continue;
-                }
-               /* Read any spd byte to see if the dimm is present */
-               value = spd_read_byte(ctrl->channel0[i], 5); /* Physical Banks */
-                       if(value < 0) continue;
-        
-               dword &= ~(1<<i);
-        }
-       
-       pci_write_config32(ctrl->d0, 0x8c, dword);
-       
-       return dimm_mask;
-}
+       // RAM_COMMAND_NORMAL is an exception. 
+       // It affects only the memory controller and does not need to be "sent" to the DIMMs.
 
-static const uint16_t cas_latency_80[] = {
-       /* For cas latency 2.0 0x01 works and until I see a large test sample
-        * I am not prepared to change this value, to the intel recommended value
-        * of 0x0d.  Eric Biederman
-        */
-       /* The E7501 requires b1 rather than 01 for CAS2 or memory will be hosed
-        * CAS 1.5 is claimed to be unsupported, will try to test that
-        * will need to determine correct values for other CAS values
-        * (perhaps b5, b1, b6?)
-        * Steven James 02/06/2003
-        */
-        
-//#    .byte 0x05, 0x01, 0x06 
-//#    .byte 0xb5, 0xb1, 0xb6 
-       0x0, 0x0bb1, 0x0662   /* RCVEN */ 
-};
-static const uint16_t cas_latency_80_4dimms[] = {
-        0x0, 0x0bb1, 0x0882
-};
+       if (command != RAM_COMMAND_NORMAL) {
 
+               // Send the command to all DIMMs by accessing a memory location within each
+               // NOTE: for mode select commands, some of the location address bits
+               //               are part of the command
 
-static const uint8_t cas_latency_78[] = {
-       DRT_CAS_1_5, DRT_CAS_2_0, DRT_CAS_2_5
-};
+               // Map JEDEC mode bits to E7501
+               if (command == RAM_COMMAND_MRS) {
+                       // Host address lines [15:5] map to DIMM address lines [12:11, 9:1]
+                       // The E7501 hard-sets DIMM address lines 10 & 0 to zero
 
-static long spd_set_cas_latency(const struct mem_controller *ctrl, long dimm_mask) {
-       /* Walk through all dimms and find the interesection of the
-        * supported cas latencies.
-        */
-        int i;
-        /* Initially allow cas latencies 2.5, 2.0
-         * which the chipset supports.
-         */
-       uint32_t dword = (1<<3)| (1<<2);// esi
-       uint32_t edi;
-       uint32_t ecx;
-       unsigned device;
-       int value;
-       uint8_t byte;
-       uint16_t word;
+                       ASSERT(!(jedec_mode_bits & 0x0401));
+
+                       e7501_mode_bits = ((jedec_mode_bits & 0x1800) << (15-12)) |             // JEDEC bits 11-12 move to bits 14-15
+                                                         ((jedec_mode_bits & 0x03FE) << (13-9));               // JEDEC bits 1-9 move to bits 5-13
+
+               } else if (command == RAM_COMMAND_EMRS) {
+                       // Host address lines [15:3] map to DIMM address lines [12:0]
+                       e7501_mode_bits = jedec_mode_bits <<= 3;
+               } else
+                       ASSERT(jedec_mode_bits == 0);
+
+
+               dimm_start_64M_multiple = 0;
+
+               for (i = 0; i < (MAX_NUM_CHANNELS * MAX_DIMM_SOCKETS_PER_CHANNEL); ++i) {
+
+                       uint8_t dimm_end_64M_multiple = pci_read_config8(ctrl->d0, DRB_ROW_0 + i);
+                       if (dimm_end_64M_multiple > dimm_start_64M_multiple) {
+
+                               // This code assumes DRAM row boundaries are all set below 4 GB
+                               // NOTE: 0x40 * 64 MB == 4 GB
+                               ASSERT(dimm_start_64M_multiple < 0x40);
+
+                               // NOTE: 2^26 == 64 MB 
+
+                               uint32_t dimm_start_address = dimm_start_64M_multiple << 26;
+
+                               RAM_DEBUG_MESSAGE("    Sending RAM command to 0x");
+                               RAM_DEBUG_HEX32(dimm_start_address + e7501_mode_bits);
+                               RAM_DEBUG_MESSAGE("\r\n");
+                               read32(dimm_start_address + e7501_mode_bits);
 
+                               // Set the start of the next DIMM
+                               dimm_start_64M_multiple = dimm_end_64M_multiple;
+                       }
+               }
+       }
+}
+
+//----------------------------------------------------------------------------------
+// Function:           set_ram_mode
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+//                                     jedec_mode_bits - for mode register set & extended mode register set
+//                                             commands, bits 0-12 contain the register value in JEDEC format.
+// Return Value:       None
+// Description:        Set the mode register of all DIMMs. The proper CAS# latency 
+//                                     setting is added to the mode bits specified by the caller.
+//
+static void set_ram_mode(const struct mem_controller *ctrl, uint16_t jedec_mode_bits)
+{
+       ASSERT(!(jedec_mode_bits & SDRAM_CAS_MASK));
+
+       uint32_t dram_cas_latency = pci_read_config32(ctrl->d0, DRT) & DRT_CAS_MASK;
        
-        for(i = 0; i < DIMM_SOCKETS; i++) {
-               if (!(dimm_mask & (1 << i))) {
-                        continue;
-                }
-               value = spd_read_byte(ctrl->channel0[i], 18);
-               if(value < 0) continue;
-               /* Find the highest supported cas latency */
-               ecx = log2(value & 0xff); 
-               edi = (1<< ecx);
-
-                /* Remember the supported cas latencies */
-               ecx = (value & 0xff);
-
-               /* Verify each cas latency at 133Mhz */
-               /* Verify slowest/highest CAS latency */
-               value = spd_read_byte(ctrl->channel0[i], 9);
-               if(value < 0 ) continue;
-               if(value > 0x75 ) {     
-                       /* The bus is too fast so we cannot support this case latency */
-                       ecx &= ~edi;
+       switch (dram_cas_latency) {
+       case DRT_CAS_2_5:
+               jedec_mode_bits |= SDRAM_CAS_2_5;
+               break;
+
+       case DRT_CAS_2_0:
+               jedec_mode_bits |= SDRAM_CAS_2_0;
+               break;
+
+       default:
+               BUG();
+               break;
+       }
+
+       do_ram_command(ctrl, RAM_COMMAND_MRS, jedec_mode_bits);
+}
+
+/*^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^*/
+/*                                                     SDRAM CONFIGURATION FUNCTIONS                                             */
+/**********************************************************************************/
+
+//----------------------------------------------------------------------------------
+// Function:           configure_dimm_row_boundaries
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+//                                     dimm_log2_num_bits - log2(number of bits) for each side of the DIMM
+//                                     total_dram_64M_multiple - total DRAM in the system (as a 
+//                                             multiple of 64 MB) for DIMMs < dimm_index
+//                                     dimm_index - which DIMM pair is being processed 
+//                                                              (0..MAX_DIMM_SOCKETS_PER_CHANNEL)
+// Return Value:       New multiple of 64 MB total DRAM in the system
+// Description:        Configure the E7501's DRAM Row Boundary registers for the memory
+//                                     present in the specified DIMM.
+//
+static uint8_t configure_dimm_row_boundaries(const struct mem_controller *ctrl, 
+                                                                                        struct dimm_size dimm_log2_num_bits, 
+                                                                                        uint8_t total_dram_64M_multiple, 
+                                                                                        unsigned dimm_index)
+{
+       int i;
+
+       ASSERT(dimm_index < MAX_DIMM_SOCKETS_PER_CHANNEL);
+
+       // DIMM sides must be at least 32 MB
+       ASSERT(dimm_log2_num_bits.side1 >= 28);
+       ASSERT((dimm_log2_num_bits.side2 == 0) || (dimm_log2_num_bits.side2 >= 28));
+
+       // In dual-channel mode, we are called only once for each pair of DIMMs. 
+       // Each time we process twice the capacity of a single DIMM.
+
+       // Convert single DIMM capacity to paired DIMM capacity
+       // (multiply by two ==> add 1 to log2)
+       dimm_log2_num_bits.side1++;
+       if (dimm_log2_num_bits.side2 > 0)
+               dimm_log2_num_bits.side2++;
+              
+       // Add the capacity of side 1 this DIMM pair (as a multiple of 64 MB)
+       // to the total capacity of the system
+       // NOTE: 64 MB == 512 Mb, and log2(512 Mb) == 29
+
+       total_dram_64M_multiple += (1 << (dimm_log2_num_bits.side1 - 29));
+
+       // Configure the boundary address for the row on side 1
+       pci_write_config8(ctrl->d0, DRB_ROW_0+(dimm_index<<1), total_dram_64M_multiple);
+
+       // If the DIMMs are double-sided, add the capacity of side 2 this DIMM pair 
+       // (as a multiple of 64 MB) to the total capacity of the system
+    if (dimm_log2_num_bits.side2 >= 29)
+               total_dram_64M_multiple += (1 << (dimm_log2_num_bits.side2 - 29));
+        
+       // Configure the boundary address for the row (if any) on side 2
+    pci_write_config8(ctrl->d0, DRB_ROW_1+(dimm_index<<1), total_dram_64M_multiple);
+
+       // Update boundaries for rows subsequent to these.
+       // These settings will be overridden by a subsequent call if a populated physical slot exists
+        
+    for(i=dimm_index+1; i<MAX_DIMM_SOCKETS_PER_CHANNEL; i++) {
+               pci_write_config8(ctrl->d0, DRB_ROW_0+(i<<1), total_dram_64M_multiple);
+        pci_write_config8(ctrl->d0, DRB_ROW_1+(i<<1), total_dram_64M_multiple);
+       }
+        
+    return total_dram_64M_multiple;
+}
+
+//----------------------------------------------------------------------------------
+// Function:           configure_e7501_ram_addresses
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+//                                     dimm_mask - bitmask of populated DIMMs on the board - see 
+//                                                             spd_get_supported_dimms()
+// Return Value:       None
+// Description:        Program the E7501's DRAM row boundary addresses and its Top Of 
+//                                     Low Memory (TOLM). If necessary, set up a remap window so we 
+//                                     don't waste DRAM that ordinarily would lie behind addresses 
+//                                     reserved for memory-mapped I/O.
+//
+static void configure_e7501_ram_addresses(const struct mem_controller *ctrl, 
+                                                                                 uint8_t dimm_mask)
+{
+       int i;
+    uint8_t total_dram_64M_multiple = 0;
+
+       // Configure the E7501's DRAM row boundaries
+       // Start by zeroing out the temporary initial configuration
+       pci_write_config32(ctrl->d0, DRB_ROW_0, 0);
+       pci_write_config32(ctrl->d0, DRB_ROW_4, 0);
+
+       for(i = 0; i < MAX_DIMM_SOCKETS_PER_CHANNEL; i++) {
+
+        uint16_t dimm_socket_address = ctrl->channel0[i];
+               struct dimm_size sz;
+
+        if (!(dimm_mask & (1 << i)))
+                       continue;               // This DIMM not present
+
+        sz = spd_get_dimm_size(dimm_socket_address);
+
+        RAM_DEBUG_MESSAGE("dimm size =");
+        RAM_DEBUG_HEX32(sz.side1);
+        RAM_DEBUG_MESSAGE(" ");
+        RAM_DEBUG_HEX32(sz.side2);
+        RAM_DEBUG_MESSAGE("\r\n");
+
+               if (sz.side1 == 0)
+                       die("Bad SPD value\r\n");
+
+               total_dram_64M_multiple = configure_dimm_row_boundaries(ctrl, sz, total_dram_64M_multiple, i);
+       }
+
+       // Configure the Top Of Low Memory (TOLM) in the E7501
+       // This address must be a multiple of 128 MB that is less than 4 GB.
+       // NOTE: 16-bit wide TOLM register stores only the highest 5 bits of a 32-bit address
+       //               in the highest 5 bits.
+
+       // We set TOLM to the smaller of 0xC0000000 (3 GB) or the total DRAM in the system.
+       // This reserves addresses from 0xC0000000 - 0xFFFFFFFF for non-DRAM purposes
+       // such as flash and memory-mapped I/O.
+
+       // If there is more than 3 GB of DRAM, we define a remap window which
+       // makes the DRAM "behind" the reserved region available above the top of physical
+       // memory.
+
+       // NOTE: 0xC0000000 / (64 MB) == 0x30
+
+    if (total_dram_64M_multiple <= 0x30)  {
+
+               // <= 3 GB total RAM
+
+               /* I should really adjust all of this in C after I have resources
+         * to all of the pci devices.
+         */
+
+               // Round up to 128MB granularity
+               // SJM: Is "missing" 64 MB of memory a potential issue? Should this round down?
+
+               uint8_t total_dram_128M_multiple = (total_dram_64M_multiple + 1) >> 1;
+
+               // Convert to high 16 bits of address
+               uint16_t top_of_low_memory = total_dram_128M_multiple << 11;
+
+        pci_write_config16(ctrl->d0, TOLM, top_of_low_memory);
+
+       } else {
+
+               // > 3 GB total RAM
+
+               // Set defaults for > 4 GB DRAM, i.e. remap a 1 GB (= 0x10 * 64 MB) range of memory
+               uint16_t remap_base = total_dram_64M_multiple;                          // A[25:0] == 0
+               uint16_t remap_limit = total_dram_64M_multiple + 0x10 - 1;      // A[25:0] == 0xF
+
+               // Put TOLM at 3 GB
+
+               pci_write_config16(ctrl->d0, TOLM, 0xc000);
+
+               // Define a remap window to make the RAM that would appear from 3 GB - 4 GB
+               // visible just beyond 4 GB or the end of physical memory, whichever is larger
+               // NOTE: 16-bit wide REMAP registers store only the highest 10 bits of a 36-bit address,
+               //               (i.e. a multiple of 64 MB) in the lowest 10 bits.
+               // NOTE: 0x100000000 / (64 MB) == 0x40
+
+        if (total_dram_64M_multiple < 0x40) {
+                       remap_base = 0x40;              // 0x100000000
+                       remap_limit = 0x40 + (total_dram_64M_multiple - 0x30) - 1;
                }
 
-               /* Verify the highest CAS latency - 0.5 clocks */
-               edi >>= 1;
-               if(edi != 0) {
-                       value = spd_read_byte(ctrl->channel0[i], 23);
-                       if(value < 0 ) continue;
-                       if(value > 0x75) {
-                               /* The bus is too fast so we cannot support this cas latency */
-                               ecx &= ~edi;
-                       }
+        pci_write_config16(ctrl->d0, REMAPBASE, remap_base);
+        pci_write_config16(ctrl->d0, REMAPLIMIT, remap_limit);
+       }
+}
+
+//----------------------------------------------------------------------------------
+// Function:           initialize_ecc
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+// Return Value:       None
+// Description:        If we're configured to use ECC, initialize the SDRAM and
+//                                     clear the E7501's ECC error flags.
+//
+static void initialize_ecc(const struct mem_controller *ctrl)
+{
+       uint32_t dram_controller_mode;
+
+       /* Test to see if ECC support is enabled */
+       dram_controller_mode = pci_read_config32(ctrl->d0, DRC);
+       dram_controller_mode >>= 20;
+       dram_controller_mode &= 3;
+       if (dram_controller_mode == 2)  {
+               
+               uint8_t byte;
+
+               RAM_DEBUG_MESSAGE("Initializing ECC state...\r\n");
+               /* Initialize ECC bits , use ECC zero mode (new to 7501)*/
+               pci_write_config8(ctrl->d0, MCHCFGNS, 0x06);
+               pci_write_config8(ctrl->d0, MCHCFGNS, 0x07);
+
+               // Wait for scrub cycle to complete
+               do {
+                       byte = pci_read_config8(ctrl->d0, MCHCFGNS);
+
+               } while ( (byte & 0x08 ) == 0);
+
+               pci_write_config8(ctrl->d0, MCHCFGNS, byte & 0xfc);
+               RAM_DEBUG_MESSAGE("ECC state initialized.\r\n");        
+
+               /* Clear the ECC error bits */
+               pci_write_config8(ctrl->d0f1, DRAM_FERR, 0x03);
+               pci_write_config8(ctrl->d0f1, DRAM_NERR, 0x03);
+
+               // Clear DRAM Interface error bits (write-one-clear)
+               pci_write_config32(ctrl->d0f1, FERR_GLOBAL, 1<<18); 
+           pci_write_config32(ctrl->d0f1, NERR_GLOBAL, 1<<18);
+
+               // Start normal ECC scrub
+               pci_write_config8(ctrl->d0, MCHCFGNS, 5);
+       }
+       
+}
+
+//----------------------------------------------------------------------------------
+// Function:           configure_e7501_dram_timing
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+//                                     dimm_mask - bitmask of populated DIMMs on the board - see 
+//                                                             spd_get_supported_dimms()
+// Return Value:       None
+// Description:        Program the DRAM Timing register of the E7501 (except for CAS# 
+//                                     latency, which is assumed to have been programmed already), based 
+//                                     on the parameters of the various installed DIMMs.
+//
+static void configure_e7501_dram_timing(const struct mem_controller *ctrl, uint8_t dimm_mask) 
+{
+       int i;
+    uint32_t dram_timing;
+    int value;
+       uint8_t slowest_row_precharge = 0;
+       uint8_t slowest_ras_cas_delay = 0;
+       uint8_t slowest_active_to_precharge_delay = 0;
+       uint32_t current_cas_latency = pci_read_config32(ctrl->d0, DRT) & DRT_CAS_MASK;
+
+       // CAS# latency must be programmed beforehand
+       ASSERT((current_cas_latency == DRT_CAS_2_0) || (current_cas_latency == DRT_CAS_2_5));
+
+       // Each timing parameter is determined by the slowest DIMM
+
+       for (i = 0; i < MAX_DIMM_SOCKETS; i++) {
+
+        uint16_t dimm_socket_address;
+       
+               if (!(dimm_mask & (1 << i)))
+                       continue;               // This DIMM not present
+
+               if (i < MAX_DIMM_SOCKETS_PER_CHANNEL)
+                       dimm_socket_address = ctrl->channel0[i];
+               else
+                       dimm_socket_address = ctrl->channel1[i - MAX_DIMM_SOCKETS_PER_CHANNEL];
+
+        value = spd_read_byte(dimm_socket_address, SPD_MIN_ROW_PRECHARGE_TIME);
+        if (value < 0) goto hw_err;
+               if (value > slowest_row_precharge)
+                       slowest_row_precharge = value;
+
+               value = spd_read_byte(dimm_socket_address, SPD_MIN_RAS_TO_CAS_DELAY);
+               if(value < 0 ) goto hw_err;
+               if (value > slowest_ras_cas_delay)
+                       slowest_ras_cas_delay = value;
+
+               value = spd_read_byte(dimm_socket_address, SPD_MIN_ACTIVE_TO_PRECHARGE_DELAY);
+               if(value < 0 ) goto hw_err;
+               if (value > slowest_active_to_precharge_delay)
+                       slowest_active_to_precharge_delay = value;
+       }
+
+       // NOTE for timing parameters:
+       //              At 133 MHz, 1 clock == 7.52 ns
+
+    /* Read the initial state */
+    dram_timing = pci_read_config32(ctrl->d0, DRT);
+
+       /* Trp */
+
+       // E7501 supports only 2 or 3 clocks for tRP
+       if (slowest_row_precharge > ((22<<2) | (2<<0)))
+               die("unsupported DIMM tRP");                    // > 22.5 ns: 4 or more clocks
+       else if (slowest_row_precharge > (15<<2))
+               dram_timing &= ~(1<<0);                                 // > 15.0 ns: 3 clocks 
+       else
+               dram_timing |= (1<<0);                                  // <= 15.0 ns: 2 clocks
+
+       /*  Trcd */
+
+       // E7501 supports only 2 or 3 clocks for tRCD
+       // Use the same value for both read & write
+       dram_timing &= ~((1<<3)|(3<<1));
+       if (slowest_ras_cas_delay > ((22<<2) | (2<<0)))
+               die("unsupported DIMM tRCD");                   // > 22.5 ns: 4 or more clocks
+       else if (slowest_ras_cas_delay > (15<<2))
+               dram_timing |= (2<<1);                                  // > 15.0 ns: 3 clocks 
+       else
+               dram_timing |= ((1<<3) | (3<<1));               // <= 15.0 ns: 2 clocks
+
+       /* Tras */
+
+       // E7501 supports only 5, 6, or 7 clocks for tRAS
+       // 5 clocks ~= 37.6 ns, 6 clocks ~= 45.1 ns, 7 clocks ~= 52.6 ns
+       dram_timing &= ~(3<<9);
+
+       if (slowest_active_to_precharge_delay > 52)
+               die("unsupported DIMM tRAS");                                   // > 52 ns:      8 or more clocks
+       else if (slowest_active_to_precharge_delay > 45)
+               dram_timing |= (0<<9);                                                  // 46-52 ns: 7 clocks 
+       else if (slowest_active_to_precharge_delay > 37)
+               dram_timing |= (1<<9);                                                  // 38-45 ns: 6 clocks
+       else
+               dram_timing |= (2<<9);                                                  // < 38 ns:      5 clocks
+
+
+       /* Trd */ 
+
+       /* Set to a 7 clock read delay. This is for 133Mhz
+       *  with a CAS latency of 2.5  if 2.0 a 6 clock
+       *  delay is good  */
+
+       dram_timing &= ~(7<<24);                // 7 clocks
+       if (current_cas_latency == DRT_CAS_2_0)
+               dram_timing |= (1<<24);         // 6 clocks
+
+       /*
+        * Back to Back Read-Write Turn Around
+        */
+       /* Set to a 5 clock back to back read to write turn around.
+        *  4 is a good delay if the CAS latency is 2.0 */
+
+       dram_timing &= ~(1<<28);                // 5 clocks
+       if (current_cas_latency == DRT_CAS_2_0)
+               dram_timing |= (1<<28);         // 4 clocks
+
+       pci_write_config32(ctrl->d0, DRT, dram_timing);
+
+       return;
+
+hw_err:
+       die(SPD_ERROR);
+}
+
+//----------------------------------------------------------------------------------
+// Function:           configure_e7501_cas_latency
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+//                                     dimm_mask - bitmask of populated DIMMs on the board - see 
+//                                                             spd_get_supported_dimms()
+// Return Value:       None
+// Description:        Determine the shortest CAS# latency that the E7501 and all DIMMs
+//                                     have in common, and program the E7501 to use it.
+//
+static void configure_e7501_cas_latency(const struct mem_controller *ctrl, uint8_t dimm_mask) 
+{
+       int i;
+       int value;
+       uint32_t dram_timing;
+       uint16_t maybe_dram_read_timing;
+       uint32_t dword;
+
+       // CAS# latency bitmasks in SPD_ACCEPTABLE_CAS_LATENCIES format
+       // NOTE: E7501 supports only 2.0 and 2.5
+       uint32_t system_compatible_cas_latencies = SPD_CAS_LATENCY_2_0 | SPD_CAS_LATENCY_2_5;
+       uint32_t current_cas_latency;
+       uint32_t dimm_compatible_cas_latencies;
+       
+       for (i = 0; i < MAX_DIMM_SOCKETS; i++) {
+
+        uint16_t dimm_socket_address;
+
+               if (!(dimm_mask & (1 << i)))
+                       continue;               // This DIMM not usable
+
+               if (i < MAX_DIMM_SOCKETS_PER_CHANNEL)
+                       dimm_socket_address = ctrl->channel0[i];
+               else
+                       dimm_socket_address = ctrl->channel1[i - MAX_DIMM_SOCKETS_PER_CHANNEL];
+
+               value = spd_read_byte(dimm_socket_address, SPD_ACCEPTABLE_CAS_LATENCIES);
+               if (value < 0) goto hw_err;
+
+        dimm_compatible_cas_latencies = value & 0x7f;                                          // Start with all supported by DIMM
+               current_cas_latency = 1 << log2(dimm_compatible_cas_latencies);         // Max supported by DIMM
+
+               // Can we support the highest CAS# latency?
+
+               value = spd_read_byte(dimm_socket_address, SPD_MIN_CYCLE_TIME_AT_CAS_MAX);
+               if (value < 0) goto hw_err;
+
+               // NOTE: At 133 MHz, 1 clock == 7.52 ns
+               if (value > 0x75) {
+                       // Our bus is too fast for this CAS# latency
+                       // Remove it from the bitmask of those supported by the DIMM that are compatible
+                       dimm_compatible_cas_latencies &= ~current_cas_latency;
+               }
+
+               // Can we support the next-highest CAS# latency (max - 0.5)?
+
+               current_cas_latency >>= 1;
+               if (current_cas_latency != 0) {
+                       value = spd_read_byte(dimm_socket_address, SPD_MIN_CYCLE_TIME_AT_CAS_REDUCED_05);
+                       if(value < 0 ) goto hw_err;
+                       if(value > 0x75)
+                               dimm_compatible_cas_latencies &= ~current_cas_latency;
                }
 
-               /* Verify the highest CAS latency - 1.0 clocks */
-               edi >>=1;
-               if(edi !=0) {
-                        value = spd_read_byte(ctrl->channel0[i], 25);
-                        if(value < 0 ) continue;
-                        if(value > 0x75) {
-                                /* The bus is too fast so we cannot support this cas latency */
-                                ecx &= ~edi;
-                        }
+               // Can we support the next-highest CAS# latency (max - 1.0)?
+               current_cas_latency >>= 1;
+               if (current_cas_latency != 0) {
+                       value = spd_read_byte(dimm_socket_address, SPD_MIN_CYCLE_TIME_AT_CAS_REDUCED_10);
+            if(value < 0 ) goto hw_err;
+            if(value > 0x75)
+                dimm_compatible_cas_latencies &= ~current_cas_latency;
                }
 
-               /* Now find which cas latencies are supported for the bus */
-               dword &= ecx;
+               // Restrict the system to CAS# latencies compatible with this DIMM
+               system_compatible_cas_latencies &= dimm_compatible_cas_latencies;
+
        /* go to the next DIMM */
        }
 
        /* After all of the arduous calculation setup with the fastest
         * cas latency I can use.
         */
-       value = log2f(dword);  // bsrl = log2 how about bsfl?
-       if(value ==0 ) return -1;
-       ecx = value -1;
 
-       byte = pci_read_config8(ctrl->d0, 0x78);
-       byte &= ~(DRT_CAS_MASK);
-       byte |= cas_latency_78[ecx];
-       pci_write_config8(ctrl->d0,0x78, byte);
+       dram_timing = pci_read_config32(ctrl->d0, DRT);
+       dram_timing &= ~(DRT_CAS_MASK);
+
+       maybe_dram_read_timing = pci_read_config16(ctrl->d0, MAYBE_DRDCTL);
+       maybe_dram_read_timing &= 0xF00C;
+
+       if (system_compatible_cas_latencies & SPD_CAS_LATENCY_2_0) {
+               dram_timing |= DRT_CAS_2_0;
+               maybe_dram_read_timing |= 0xBB1;
+       }
+       else if (system_compatible_cas_latencies & SPD_CAS_LATENCY_2_5) {
+
+               uint32_t dram_row_attributes = pci_read_config32(ctrl->d0, DRA);
+
+               dram_timing |= DRT_CAS_2_5;
+
+               // At CAS# 2.5, DRAM Read Timing (if that's what it its) appears to need a slightly
+               // different value if all DIMM slots are populated
+
+               if ((dram_row_attributes & 0xff)         && (dram_row_attributes & 0xff00) && 
+                       (dram_row_attributes & 0xff0000) && (dram_row_attributes & 0xff000000)) {
+
+                       // All slots populated
+                       maybe_dram_read_timing |= 0x0882;
+               } 
+               else {
+                       // Some unpopulated slots
+                       maybe_dram_read_timing |= 0x0662;
+               }
+       }
+       else
+               die("No CAS# latencies compatible with all DIMMs!!\r\n");
+
+       pci_write_config32(ctrl->d0, DRT, dram_timing);
 
        /* set master DLL reset */
        dword = pci_read_config32(ctrl->d0, 0x88);
        dword |= (1<<26);
-       
-       /* the rest of the references are words */
-//     ecx<<=1;  // don't need shift left, because we already define that in u16 array
        pci_write_config32(ctrl->d0, 0x88, dword);
        
-       
-       dword &= 0x0c0000ff;    /* patch try register 88 is undocumented tnz */
+       dword &= 0x0c0007ff;    /* patch try register 88 is undocumented tnz */
        dword |= 0xd2109800;
 
        pci_write_config32(ctrl->d0, 0x88, dword);
+
        
-       word = pci_read_config16(ctrl->d0, 0x80);
-       word &= ~(0x0fff);
-       word |= cas_latency_80[ecx];
-
-       dword = pci_read_config32(ctrl->d0, 0x70);
-
-       if((dword & 0xff) !=0 ) {
-               dword >>=8;
-               if((dword & 0xff)!=0) {
-                       dword >>=8;
-                       if((dword & 0xff)!=0) {
-                               dword >>= 8;
-                               if( (dword & 0xff)!=0) {
-                                       word &=~(0x0fff);  /* we have dimms in all 4 slots */ 
-                                       word |=cas_latency_80_4dimms[ecx];
-                               }
-                       }
-               }
-       }
-       
-       pci_write_config16(ctrl->d0, 0x80, word);
+       pci_write_config16(ctrl->d0, MAYBE_DRDCTL, maybe_dram_read_timing);
        
        dword = pci_read_config32(ctrl->d0, 0x88);      /* reset master DLL reset */
        dword &= ~(1<<26);
        pci_write_config32(ctrl->d0, 0x88, dword);
-       
-       RAM_RESET_DDR_PTR(ctrl);
 
-       return dimm_mask;
+       return;
 
+hw_err:
+       die(SPD_ERROR);
 }
 
-static long spd_set_dram_timing(const struct mem_controller *ctrl, long dimm_mask) {
-       /* Walk through all dimms and find the interesection of the
-        * supported dram timings.
-        */
+//----------------------------------------------------------------------------------
+// Function:           configure_e7501_dram_controller_mode
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+//                                     dimm_mask - bitmask of populated DIMMs on the board - see 
+//                                                             spd_get_supported_dimms()
+// Return Value:       None
+// Description:        Configure the refresh interval so that we refresh no more often
+//                                     than required by the "most needy" DIMM. Also disable ECC if any
+//                                     of the DIMMs don't support it.
+//
+static void configure_e7501_dram_controller_mode(const struct mem_controller *ctrl, 
+                                                                                                uint8_t dimm_mask) 
+{
+       int i;  
+
+       // Initial settings
+    uint32_t controller_mode = pci_read_config32(ctrl->d0, DRC);
+       uint32_t system_refresh_mode = (controller_mode >> 8) & 7;
+
+       // Code below assumes that most aggressive settings are in
+       // force when we are called, either via E7501 reset defaults
+       // or by sdram_set_registers():
+       //      - ECC enabled
+       //      - No refresh
+
+       ASSERT((controller_mode & (3<<20)) == (2<<20));         // ECC
+       ASSERT(!(controller_mode & (7 << 8)));          // Refresh
+
+    /* Walk through _all_ dimms and find the least-common denominator for:
+        *      - ECC support
+     *  - refresh rates
+     */        
+
+       for (i = 0; i < MAX_DIMM_SOCKETS; i++) {
+
+               uint32_t dimm_refresh_mode;
+           int value;
+        uint16_t dimm_socket_address;
 
-        int i;
-        uint32_t dword;
-        int value;
-
-        /* Read the inititial state */
-        dword = pci_read_config32(ctrl->d0, 0x78);
-/*
-# Intel clears top bit here, should we?
-# No the default is on and for normal timming it should be on.  Tom Z
-        andl    $0x7f, %esi
-*/
-        
-        
-        for(i = 0; i < DIMM_SOCKETS; i++) {
                if (!(dimm_mask & (1 << i))) {
-                        continue;
-                }
-               /* Trp */
-                value = spd_read_byte(ctrl->channel0[i], 27);
-                if(value < 0) continue;
-               if(value > (15<<2)) {
-                       /* At 133Mhz if row precharge time is above than 15ns than we
-                        * need 3 clocks not 2 clocks.
-                       */
-                       dword &= ~(1<<0); 
+                       continue;               // This DIMM not usable
+        }
+
+               if (i < MAX_DIMM_SOCKETS_PER_CHANNEL)
+                       dimm_socket_address = ctrl->channel0[i];
+               else
+                       dimm_socket_address = ctrl->channel1[i - MAX_DIMM_SOCKETS_PER_CHANNEL];
+
+               // Disable ECC mode if any one of the DIMMs does not support ECC
+               // SJM: Should we just die here? E7501 datasheet says non-ECC DIMMs aren't supported.
+
+               value = spd_read_byte(dimm_socket_address, SPD_DIMM_CONFIG_TYPE);
+        die_on_spd_error(value);
+               if (value != ERROR_SCHEME_ECC) {
+                       controller_mode &= ~(3 << 20);
                }
-               /*  Trcd */
-               value = spd_read_byte(ctrl->channel0[i],29);
-               if(value < 0 ) continue;
-               if(value > (15<<2)) {
-                       /* At 133Mhz if the Minimum ras to cas delay is about 15ns we
-                        * need 3 clocks not 2 clocks.
-                       */
-                       dword &= ~((1<<3)|(1<<1));
+
+               value = spd_read_byte(dimm_socket_address, SPD_REFRESH);
+               die_on_spd_error(value);
+               value &= 0x7f;          // Mask off self-refresh bit
+               if(value > MAX_SPD_REFRESH_RATE) { 
+                       print_err("unsupported refresh rate\r\n");
+                       continue;
                }
-               /* Tras */
-               value = spd_read_byte(ctrl->channel0[i],30);
-               if(value < 0 ) continue;
-                       /* Convert tRAS from ns to 133Mhz clock cycles */
-               value <<=1;      /* mult by 2 to make 7.5 15 */
-               value  += 15;   /* Make certain we round up */
-               value --;
-               value &= 0xff;  /* Clear the upper bits of eax */
-               value /= 15;
                
-               /* Don't even process small timings */
-               if(value >5) {
-                       uint32_t tmp;
-                       /* Die if the value is to large */
-                       if(value>7) {
-                               die ("unsupported_rcd\r\n");
-                       }
-                       /* Convert to clocks - 5 */
-                       value -=5;
-                       /* Convert the existing value into clocks - 5 */
-                       tmp = (~((dword>>9) & 3) - 1) & 3;
-                       /* See if we need a slower timing */
-                       if(value > tmp ) {
-                               /* O.k. put in our slower timing */
-                               dword &= ~(3<<9);
-                               dword |= ((~(value + 1)) & 3)<<9 ;
-                       }
-               }
-       
-               /* Trd */ 
-               /* Set to a 7 clock read delay. This is for 133Mhz
-               *  with a CAS latency of 2.5  if 2.0 a 6 clock
-               *  delay is good  */
-               if( (pci_read_config8(ctrl->d0, 0x78) & 0x30) ==0 ){
-                       dword &= ~(7<<24); /* CAS latency is 2.5, make 7 clks */
+               // Get the appropriate E7501 refresh mode for this DIMM
+               dimm_refresh_mode = refresh_rate_map[value];
+               if (dimm_refresh_mode > 7) {
+                       print_err("unsupported refresh rate\r\n");
+                       continue;
                }
 
-               /*
-               * Back to Back Read Turn Around
-               */
-               /* Set to a 3 clock back to back read turn around.  This
-                *  is good for CAS latencys 2.5 and 2.0 */
-               dword |= (1<<27);
-               /*
-               * Back to Back Read-Write Turn Around
-               */
-               /* Set to a 5 clock back to back read to write turn around.
-               *  4 is a good delay if the CAS latency is 2.0 */
-               if( ( pci_read_config8(ctrl->d0, 0x78) & (1<<4)) == 0) {
-                       dword &= ~(1<<28);
+               // If this DIMM requires more frequent refresh than others,
+               // update the system setting
+               if (refresh_frequency[dimm_refresh_mode] > refresh_frequency[system_refresh_mode])
+                       system_refresh_mode = dimm_refresh_mode;
+               
+#ifdef SUSPICIOUS_LOOKING_CODE
+// SJM NOTE: This code doesn't look right. SPD values are an order of magnitude smaller
+//                      than the clock period of the memory controller. Also, no other northbridge
+//                      looks at SPD_ADDRESS_CMD_HOLD.
+
+               // Switch to 2 clocks for address/command if required by any one of the DIMMs
+               // NOTE: At 133 MHz, 1 clock == 7.52 ns
+               value = spd_read_byte(dimm_socket_address, SPD_ADDRESS_CMD_HOLD);
+               die_on_spd_error(value);
+               if(value >= 0xa0) {             /* At 133MHz this constant should be 0x75 */
+                       controller_mode &= ~(1<<16);    /* Use two clock cyles instead of one */
                }
-               /*
-               * Back to Back Write-Read Turn Around
-               */
-               /* Set to a 2 clock back to back write to read turn around.
-               *  This is good for 2.5 and 2.0 CAS Latencies. */
-               dword |= (1<<29);
-       }
-       
-       pci_write_config32(ctrl->d0, 0x78, dword);
-       
-       return dimm_mask;
-
-}
-static unsigned int spd_detect_dimms(const struct mem_controller *ctrl)
-{               
-        unsigned dimm_mask;
-        int i;  
-        dimm_mask = 0;  
-#if DEBUG_RAM_CONFIG
-       print_debug("spd_detect_dimms:\r\n");
-#endif
-        for(i = 0; i < DIMM_SOCKETS; i++) {
-                int byte;
-                unsigned device;
-#if DEBUG_RAM_CONFIG
-               print_debug_hex32(i);
-               print_debug("\r\n");
-#endif
-                device = ctrl->channel0[i];
-                if (device) {
-                        byte = spd_read_byte(ctrl->channel0[i], 2);  /* Type */
-                        if (byte == 7) {
-                                dimm_mask |= (1 << i);
-                        }
-                }
-#if 1
-                device = ctrl->channel1[i];
-                if (device) {
-                        byte = spd_read_byte(ctrl->channel1[i], 2);
-                        if (byte == 7) {
-                                dimm_mask |= (1 << (i + DIMM_SOCKETS));
-                        }
-                }
 #endif
-        }       
-#if 1
-       i = (dimm_mask>>DIMM_SOCKETS);
-       if(i != (dimm_mask & ( (1<<DIMM_SOCKETS) - 1) ) ) {
-               die("now we only support dual channel\r\n");
+       
+       /* go to the next DIMM */
        }
 
-#endif
+       controller_mode |= (system_refresh_mode << 8);
 
-        return dimm_mask;
-}               
+       // Configure the E7501
+       pci_write_config32(ctrl->d0, DRC, controller_mode);
+}
 
-static uint32_t set_dimm_size(const struct mem_controller *ctrl, struct dimm_size sz, uint32_t memsz, unsigned index)
+//----------------------------------------------------------------------------------
+// Function:           configure_e7501_row_attributes
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+//                                     dimm_mask - bitmask of populated DIMMs on the board - see 
+//                                                             spd_get_supported_dimms()
+// Return Value:       None
+// Description:        Configure the E7501's DRAM Row Attributes (DRA) registers
+//                                     based on DIMM parameters read via SPD. This tells the controller
+//                                     the width of the SDRAM chips on each DIMM side (x4 or x8) and
+//                                     the page size of each DIMM side (4, 8, 16, or 32 KB).
+//
+static void configure_e7501_row_attributes(const struct mem_controller *ctrl, 
+                                                                                  uint8_t dimm_mask) 
 {
-        int i;
-        uint32_t base0, base1;
-        uint32_t dch;
-       uint8_t byte;
+       int i;
+       uint32_t row_attributes = 0;
+        
+    for (i = 0; i < MAX_DIMM_SOCKETS_PER_CHANNEL; i++) {
 
-        /* Double the size if we are using dual channel memory */
-//        if (is_dual_channel(ctrl)) {
-                /* Since I have 2 identical channels double the sizes */
-                sz.side1++ ;
-                sz.side2++;
-//        }
-              
-       if (sz.side1 != sz.side2) {
-                sz.side2 = 0;
-        } 
-        /* Make certain side1 of the dimm is at least 64MB */
-        if (sz.side1 >= (25 + 4)) {
-                memsz += (1 << (sz.side1 - (25 + 4)) ) ;
-        }
-        /* Write the size of side 1 of the dimm */
-       byte = memsz;
-        pci_write_config8(ctrl->d0, 0x60+(index<<1), byte);
+        uint16_t dimm_socket_address = ctrl->channel0[i];
+               struct dimm_size        page_size;
+               struct dimm_size        sdram_width;
 
-        /* Make certain side2 of the dimm is at least 64MB */
-        if (sz.side2 >= (25 + 4)) {
-                memsz += (1 << (sz.side2 - (25 + 4)) ) ;
-        }
-        
-         /* Write the size of side 2 of the dimm */
-       byte = memsz;
-        pci_write_config8(ctrl->d0, 0x61+(index<<1), byte);
-        
-        /* now, fill in DRBs where no physical slot exists */
-        
-        for(i=index+1;i<4;i++) {
-                pci_write_config8(ctrl->d0, 0x60+(i<<1),byte);
-                pci_write_config8(ctrl->d0, 0x61+(i<<1),byte);
-        
-        }
-        
-        return memsz;
+               if (!(dimm_mask & (1 << i)))
+                       continue;               // This DIMM not usable
 
-}
-/* LAST_DRB_SLOT is a constant for any E7500 board */
-#define LAST_DRB_SLOT 0x67
+               // Get the relevant parameters via SPD
+               page_size       = sdram_spd_get_page_size(dimm_socket_address);
+               sdram_width = sdram_spd_get_width(dimm_socket_address);
 
-static long spd_set_ram_size(const struct mem_controller *ctrl, long dimm_mask)
-{
-        int i;
-        uint32_t memsz=0;
-       uint16_t word;
-
-        for(i = 0; i < DIMM_SOCKETS; i++) {
-                struct dimm_size sz;
-                if (!(dimm_mask & (1 << i))) {
-                        continue;
-                }
-                sz = spd_get_dimm_size(ctrl->channel0[i]);
-#if DEBUG_RAM_CONFIG
-                print_debug("dimm size =");
-                print_debug_hex32(sz.side1);
-                print_debug(" ");
-                print_debug_hex32(sz.side2);
-                print_debug("\r\n");
-#endif
+               // Update the DRAM Row Attributes.
+               // Page size is encoded as log2(page size in bits) - log2(8 Kb)
+               // NOTE: 8 Kb = 2^13
+               row_attributes |= (page_size.side1 - 13) << (i<<3);                     // Side 1 of each DIMM is an EVEN row
 
-                if (sz.side1 == 0) {
-                       return -1; /* Report SPD error */
-                }
-                memsz = set_dimm_size(ctrl, sz, memsz, i);
-        }
-        /* For now hardset everything at 128MB boundaries */
-        /* %ebp has the ram size in multiples of 64MB */
-//        cmpl    $0, %ebp        /* test if there is no mem - smbus went bad */
-//        jz      no_memory_bad_smbus
-        if(memsz < 0x30)  {
-               /* I should really adjust all of this in C after I have resources
-               * to all of the pcie devices.
-               */
-
-               /* Round up to 128M granularity */
-               memsz++;
-               memsz &= 0xfe;
-               memsz<<= 10;
-               word = memsz;
-               pci_write_config16(ctrl->d0, 0xc4, word);
-        } else {
-
-               /* FIXME will this work with 3.5G of ram? */
-               /* Put TOLM at 3G */
-               pci_write_config16(ctrl->d0, 0xc4, 0xc000);
-               /* Hard code a 1G remap window, right after the ram */
-               if(memsz< 0x40){
-                       word = 0x40;  /* Ensure we are over 4G */
-               } else {
-                       word = memsz;
+               if (sdram_width.side2 > 0)
+                       row_attributes |= (page_size.side2 - 13) << ((i<<3) + 4);       // Side 2 is ODD
+
+               // Set x4 flags if appropriate
+               if (sdram_width.side1 == 4) {
+                       row_attributes |= 0x08 << (i<<3);
                }
-               pci_write_config16(ctrl->d0, 0xc6, word);
-               word += 0x10;
-               pci_write_config16(ctrl->d0, 0xc8, word);
 
+               if (sdram_width.side2 == 4) {
+                       row_attributes |= 0x08 << ((i<<3) + 4);
         }
+               
+       /* go to the next DIMM */
+       }
 
-        return dimm_mask;
+       /* Write the new row attributes register */
+       pci_write_config32(ctrl->d0, DRA, row_attributes);
 }
-                                                
-static void sdram_set_spd_registers(const struct mem_controller *ctrl) {
-       long dimm_mask;
-#if DEBUG_RAM_CONFIG
-       print_debug(spd_pre_init);
-#endif
-        //activate_spd_rom(ctrl);
-        dimm_mask = spd_detect_dimms(ctrl);
-       if (!(dimm_mask & ((1 << DIMM_SOCKETS) - 1))) {
-                print_debug("No memory for this controller\n");
-                return;
-        }
-       dimm_mask = spd_enable_clocks(ctrl, dimm_mask);
-        if (dimm_mask < 0)
-                goto hw_spd_err;
-       //spd_verify_dimms(ctrl);
-#if DEBUG_RAM_CONFIG
-       print_debug(spd_pre_set);
-#endif
-       dimm_mask = spd_set_row_attributes(ctrl,dimm_mask);
-        if (dimm_mask < 0)
-                goto hw_spd_err;
-       dimm_mask = spd_set_dram_controller_mode(ctrl,dimm_mask);
-        if (dimm_mask < 0)
-                goto hw_spd_err;       
-       dimm_mask = spd_set_cas_latency(ctrl,dimm_mask);
-        if (dimm_mask < 0)
-                goto hw_spd_err;
-       dimm_mask = spd_set_dram_timing(ctrl,dimm_mask);
-        if (dimm_mask < 0)
-                goto hw_spd_err;
-#if DEBUG_RAM_CONFIG
-       print_debug(spd_post_init);
-#endif
-       DO_DELAY        
-       spd_set_ram_size(ctrl, dimm_mask);
-               return;
- hw_spd_err:
-        /* Unrecoverable error reading SPD data */
-        print_err("SPD error - reset\r\n");
-        hard_reset();
-        return;
+
+//----------------------------------------------------------------------------------
+// Function:           enable_e7501_clocks
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+//                                     dimm_mask - bitmask of populated DIMMs on the board - see 
+//                                                             spd_get_supported_dimms()
+// Return Value:       None
+// Description:        Enable clock signals for populated DIMM sockets and disable them
+//                                     for unpopulated sockets (to reduce EMI).
+//
+static void enable_e7501_clocks(const struct mem_controller *ctrl, uint8_t dimm_mask)
+{
+       int i;
+       uint8_t clock_disable = pci_read_config8(ctrl->d0, CKDIS);
+
+       for (i = 0; i < MAX_DIMM_SOCKETS_PER_CHANNEL; i++) {
+
+               uint8_t socket_mask = 1 << i; 
+
+               if (dimm_mask & socket_mask)
+                       clock_disable &= ~socket_mask;  // DIMM present, enable clock
+               else
+                       clock_disable |= socket_mask;   // DIMM absent, disable clock
+       }
+       
+       pci_write_config8(ctrl->d0, CKDIS, clock_disable);
 }
 
 
-#define ecc_pre_init   "Initializing ECC state...\r\n"
-#define ecc_post_init  "ECC state initialized.\r\n"
-static void dram_finish(const struct mem_controller *ctrl)
+/*^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^*/
+/*                                             DIMM-DEDEPENDENT CONFIGURATION FUNCTIONS                                  */
+/**********************************************************************************/
+
+//----------------------------------------------------------------------------------
+// Function:           RAM_RESET_DDR_PTR
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+// Return Value:       None
+// Description:        DDR Receive FIFO RE-Sync (?)
+//
+static void RAM_RESET_DDR_PTR(const struct mem_controller *ctrl) 
 {
-       uint32_t dword;
        uint8_t byte;
-       /* Test to see if ECC support is enabled */
-       dword = pci_read_config32(ctrl->d0, 0x7c);
-       dword >>=20;
-       dword &=3;
-       if(dword == 2)  {
-               
-#if DEBUG_RAM_CONFIG   
-               print_debug(ecc_pre_init);
-#endif
-               /* Initialize ECC bits , use ECC zero mode (new to 7501)*/
-               pci_write_config8(ctrl->d0, 0x52, 0x06);
-               pci_write_config8(ctrl->d0, 0x52, 0x07);
-               do {
-                       byte = pci_read_config8(ctrl->d0, 0x52);
+       byte = pci_read_config8(ctrl->d0, 0x88);
+       byte |= (1 << 4);
+       pci_write_config8(ctrl->d0, 0x88, byte);
 
-               } while ( (byte & 0x08 ) == 0);
+       byte = pci_read_config8(ctrl->d0, 0x88);
+       byte &= ~(1 << 4);
+       pci_write_config8(ctrl->d0, 0x88, byte);
+}
 
-               pci_write_config8(ctrl->d0, 0x52, byte & 0xfc);
-#if DEBUG_RAM_CONFIG           
-               print_debug(ecc_post_init);     
-#endif
+//----------------------------------------------------------------------------------
+// Function:           ram_set_d0f0_regs
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+// Return Value:       None
+// Description:        Set E7501 registers that are either independent of DIMM specifics,
+//                                     or establish default settings that will be overridden when we
+//                                     learn the specifics.
+//                                     This sets PCI configuration registers to known good values based 
+//                                     on the table 'constant_register_values', which are a triple of 
+//                                     configuration register offset, mask, and bits to set.
+//
+static void ram_set_d0f0_regs(const struct mem_controller *ctrl) 
+{
+       int i;
+       int num_values = sizeof(constant_register_values)/sizeof(constant_register_values[0]);
 
-               /* Clear the ECC error bits */
-               pci_write_config8(ctrl->d0f1, 0x80, 0x03); /* dev 0, function 1, offset 80 */
-               pci_write_config8(ctrl->d0f1, 0x82, 0x03); /* dev 0, function 1, offset 82 */
+       ASSERT((num_values % 3) == 0);          // Bad table?
+
+    for(i = 0; i < num_values; i += 3) {
+
+               uint32_t register_offset = constant_register_values[i];
+               uint32_t bits_to_mask = constant_register_values[i+1];
+               uint32_t bits_to_set = constant_register_values[i+2];
+               uint32_t register_value;
+
+               // It's theoretically possible to set values for something other than D0:F0,
+               // but it's not typically done here
+               ASSERT(!(register_offset & 0xFFFFFF00));
+
+               // bits_to_mask and bits_to_set should not reference the same bits
+               // Again, not strictly an error, but flagged as a potential bug
+               ASSERT((bits_to_mask & bits_to_set) == 0);
 
-               pci_write_config32(ctrl->d0f1, 0x40, 1<<18); /* clear dev 0, function 1, offset 40; bit 18 by writing a 1 to it */
-               pci_write_config32(ctrl->d0f1, 0x44, 1<<18); /* clear dev 0, function 1, offset 44; bit 18 by writing a 1 to it */
+               register_value = pci_read_config32(ctrl->d0, register_offset);
+        register_value &= bits_to_mask;
+        register_value |= bits_to_set;
 
-               pci_write_config8(ctrl->d0, 0x52, 0x0d);
+        pci_write_config32(ctrl->d0, register_offset, register_value);
+    }
+}
+
+//----------------------------------------------------------------------------------
+// Function:           write_8dwords
+// Parameters:         src_addr
+//                                     dst_addr
+// Return Value:       None
+// Description:        Copy 64 bytes from one location to another.
+//
+static void write_8dwords(uint32_t* src_addr, uint32_t dst_addr) 
+{
+       int i;
+       for (i=0; i<8; i++) {
+               write32(dst_addr, *src_addr);
+               src_addr++;
+               dst_addr += sizeof(uint32_t);
        }
+}
+
+//----------------------------------------------------------------------------------
+// Function:           ram_set_rcomp_regs
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+// Return Value:       None
+// Description:        Set the E7501's (undocumented) RCOMP registers.
+//                                     Per the 855PM datasheet and IXP2800 HW Initialization Reference 
+//                                     Manual, RCOMP registers appear to affect drive strength, 
+//                                     pullup/pulldown offset, and slew rate of various signal groups.
+//                                     Comments below are conjecture based on apparent similarity
+//                                     between the E7501 and these two chips.
+//
+static void ram_set_rcomp_regs(const struct mem_controller *ctrl) 
+{
+       uint32_t dword;
+       uint8_t maybe_strength_control;
+
+       RAM_DEBUG_MESSAGE("Setting RCOMP registers.\r\n");
+
+       /*enable access to the rcomp bar*/
+       dword = pci_read_config32(ctrl->d0, MAYBE_MCHTST);
+    dword |= (1<<22);
+    pci_write_config32(ctrl->d0, MAYBE_MCHTST, dword);
+        
+
+       // Set the RCOMP MMIO base address
+    pci_write_config32(ctrl->d0, MAYBE_SMRBASE, RCOMP_MMIO);
+
+       // Block RCOMP updates while we configure the registers
+       dword = read32(RCOMP_MMIO + MAYBE_SMRCTL);
+       dword |= (1<<9);
+       write32(RCOMP_MMIO + MAYBE_SMRCTL, dword);
        
-       dword = pci_read_config32(ctrl->d0, 0x7c); /* FCS_EN */
-       dword |= (1<<17);
-       pci_write_config32(ctrl->d0, 0x7c, dword);
 
+       /* Begin to write the RCOMP registers */
 
-#if DEBUG_RAM_CONFIG 
-       dumpnorth();
-#endif
+       // Set CMD and DQ/DQS strength to 2x (?)
+       maybe_strength_control = read8(RCOMP_MMIO + MAYBE_DQCMDSTR) & 0x88;
+       maybe_strength_control |= 0x44;                                 
+       write8(RCOMP_MMIO + MAYBE_DQCMDSTR, maybe_strength_control);
 
-//     verify_ram();
-}
+       write_8dwords(maybe_2x_slew_table, RCOMP_MMIO + 0x80);
+       write16(RCOMP_MMIO + 0x42, 0);
 
-#if ASM_CONSOLE_LOGLEVEL > BIOS_DEBUG
-#define ram_enable_1    "Ram Enable 1\r\n"
-#define ram_enable_2   "Ram Enable 2\r\n"
-#define ram_enable_3   "Ram Enable 3\r\n"
-#define ram_enable_4   "Ram Enable 4\r\n"
-#define ram_enable_5   "Ram Enable 5\r\n"
-#define ram_enable_6   "Ram Enable 6\r\n"
-#define ram_enable_7   "Ram Enable 7\r\n"
-#define ram_enable_8   "Ram Enable 8\r\n"
-#define ram_enable_9   "Ram Enable 9\r\n"
-#define ram_enable_10  "Ram Enable 10\r\n"
-#define ram_enable_11  "Ram Enable 11\r\n"
-#endif
+       write_8dwords(maybe_1x_slew_table, RCOMP_MMIO + 0x60);
+
+       // NOTE: some factory BIOS set 0x9088 here. Seems to work either way.
+       write16(RCOMP_MMIO + 0x40, 0);
+       
+
+       // Set RCVEnOut# strength to 2x (?)
+       maybe_strength_control = read8(RCOMP_MMIO + MAYBE_RCVENSTR) & 0xF8;
+       maybe_strength_control |= 4;                                    
+       write8(RCOMP_MMIO + MAYBE_RCVENSTR, maybe_strength_control);
+
+       write_8dwords(maybe_2x_slew_table, RCOMP_MMIO + 0x1c0);
+       write16(RCOMP_MMIO + 0x50, 0);
+       
+       // Set CS# strength for x4 SDRAM to 2x (?)
+       maybe_strength_control = read8(RCOMP_MMIO + MAYBE_CSBSTR) & 0xF8;
+       maybe_strength_control |= 4;                                    
+       write8(RCOMP_MMIO + MAYBE_CSBSTR, maybe_strength_control);
+
+       write_8dwords(maybe_2x_slew_table, RCOMP_MMIO + 0x140);
+       write16(RCOMP_MMIO + 0x48, 0);
 
+       // Set CKE strength for x4 SDRAM to 2x (?)
+       maybe_strength_control = read8(RCOMP_MMIO + MAYBE_CKESTR) & 0xF8;
+       maybe_strength_control |= 4;                                    
+       write8(RCOMP_MMIO + MAYBE_CKESTR, maybe_strength_control);
+
+       write_8dwords(maybe_2x_slew_table, RCOMP_MMIO + 0xa0);
+       write16(RCOMP_MMIO + 0x44, 0);
+
+       // Set CK strength for x4 SDRAM to 1x (?)
+       maybe_strength_control = read8(RCOMP_MMIO + MAYBE_CKSTR) & 0xF8;
+       maybe_strength_control |= 1;                                    
+       write8(RCOMP_MMIO + MAYBE_CKSTR, maybe_strength_control);
+
+       write_8dwords(maybe_pull_updown_offset_table, RCOMP_MMIO + 0x180);
+       write16(RCOMP_MMIO + 0x4c, 0);
+
+       write8(RCOMP_MMIO + 0x2c, 0xff);
+
+
+       // Set the digital filter length to 8 (?)
+       dword = read32(RCOMP_MMIO + MAYBE_SMRCTL);
+
+       // NOTE: Some factory BIOS don't do this.
+       //               Doesn't seem to matter either way.
+       dword &= ~2;
+
+       dword |= 1;
+       write32(RCOMP_MMIO + MAYBE_SMRCTL, dword);
+
+       /* Wait 40 usec */
+       SLOW_DOWN_IO;
+       
+       /* unblock updates */
+       dword = read32(RCOMP_MMIO + MAYBE_SMRCTL);
+       dword &= ~(1<<9);
+       write32(RCOMP_MMIO + MAYBE_SMRCTL, dword);
+
+       // Force a RCOMP measurement cycle?
+       dword |= (1<<8);
+       write32(RCOMP_MMIO + MAYBE_SMRCTL, dword);
+       dword &= ~(1<<8);
+       write32(RCOMP_MMIO + MAYBE_SMRCTL, dword);
+       
+       /* Wait 40 usec */
+       SLOW_DOWN_IO;
+
+       /*disable access to the rcomp bar */
+       dword = pci_read_config32(ctrl->d0, MAYBE_MCHTST);
+       dword &= ~(1<<22);
+       pci_write_config32(ctrl->d0, MAYBE_MCHTST, dword);      
+
+}
+
+/*^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^*/
+/*                                     DIMM-INDEPENDENT CONFIGURATION FUNCTIONS                                          */
+/**********************************************************************************/
+
+//----------------------------------------------------------------------------------
+// Function:           sdram_enable
+// Parameters:         controllers - not used
+//                                     ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+// Return Value:       None
+// Description:        Go through the JEDEC initialization sequence for all DIMMs,
+//                                     then enable refresh and initialize ECC and memory to zero.
+//                                     Upon exit, SDRAM is up and running.
+//
 static void sdram_enable(int controllers, const struct mem_controller *ctrl)
 {
-       int i;
+       uint8_t dimm_mask = pci_read_config16(ctrl->d0, SKPD);
+       uint32_t dram_controller_mode;
+
+       if (dimm_mask == 0)
+               return;
+
        /* 1 & 2 Power up and start clocks */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_1);
-       print_debug(ram_enable_2);
-#endif
+       RAM_DEBUG_MESSAGE("Ram Enable 1\r\n");
+       RAM_DEBUG_MESSAGE("Ram Enable 2\r\n");
 
        /* A 200us delay is needed */
 
@@ -1642,32 +1826,24 @@ static void sdram_enable(int controllers, const struct mem_controller *ctrl)
        EXTRA_DELAY
 
        /* 3. Apply NOP */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_3);
-#endif
-       RAM_NOP(ctrl);
+       RAM_DEBUG_MESSAGE("Ram Enable 3\r\n");
+       do_ram_command(ctrl, RAM_COMMAND_NOP, 0);
        EXTRA_DELAY
 
        /* 4 Precharge all */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_4);
-#endif
-       RAM_PRECHARGE(ctrl);
+       RAM_DEBUG_MESSAGE("Ram Enable 4\r\n");
+       do_ram_command(ctrl, RAM_COMMAND_PRECHARGE, 0);
        EXTRA_DELAY
        
        /* wait until the all banks idle state... */
        /* 5. Issue EMRS to enable DLL */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_5);
-#endif
-       RAM_EMRS(ctrl);
+       RAM_DEBUG_MESSAGE("Ram Enable 5\r\n");
+       do_ram_command(ctrl, RAM_COMMAND_EMRS, SDRAM_EXTMODE_DLL_ENABLE | SDRAM_EXTMODE_DRIVE_NORMAL);
        EXTRA_DELAY
        
        /* 6. Reset DLL */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_6);
-#endif
-       RAM_MRS(ctrl,1);
+       RAM_DEBUG_MESSAGE("Ram Enable 6\r\n");
+       set_ram_mode(ctrl, E7501_SDRAM_MODE | SDRAM_MODE_DLL_RESET);
        EXTRA_DELAY
 
        /* Ensure a 200us delay between the DLL reset in step 6 and the final
@@ -1678,61 +1854,134 @@ static void sdram_enable(int controllers, const struct mem_controller *ctrl)
        EXTRA_DELAY
        
        /* 7 Precharge all */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_7);
-#endif
-       RAM_PRECHARGE(ctrl);
+       RAM_DEBUG_MESSAGE("Ram Enable 7\r\n");
+       do_ram_command(ctrl, RAM_COMMAND_PRECHARGE, 0);
        EXTRA_DELAY
        
        /* 8 Now we need 2 AUTO REFRESH / CBR cycles to be performed */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_8);
-#endif
-       RAM_CBR(ctrl);
+       RAM_DEBUG_MESSAGE("Ram Enable 8\r\n");
+       do_ram_command(ctrl, RAM_COMMAND_CBR, 0);
        EXTRA_DELAY
-       RAM_CBR(ctrl);
+       do_ram_command(ctrl, RAM_COMMAND_CBR, 0);
        EXTRA_DELAY
        /* And for good luck 6 more CBRs */
-       RAM_CBR(ctrl);
+       do_ram_command(ctrl, RAM_COMMAND_CBR, 0);
        EXTRA_DELAY
-       RAM_CBR(ctrl);
+       do_ram_command(ctrl, RAM_COMMAND_CBR, 0);
        EXTRA_DELAY
-       RAM_CBR(ctrl);
+       do_ram_command(ctrl, RAM_COMMAND_CBR, 0);
        EXTRA_DELAY
-       RAM_CBR(ctrl);
+       do_ram_command(ctrl, RAM_COMMAND_CBR, 0);
        EXTRA_DELAY
-       RAM_CBR(ctrl);
+       do_ram_command(ctrl, RAM_COMMAND_CBR, 0);
        EXTRA_DELAY
-       RAM_CBR(ctrl);
+       do_ram_command(ctrl, RAM_COMMAND_CBR, 0);
        EXTRA_DELAY
 
        /* 9 mode register set */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_9);
-#endif
-       RAM_MRS(ctrl,0);
+       RAM_DEBUG_MESSAGE("Ram Enable 9\r\n");
+       set_ram_mode(ctrl, E7501_SDRAM_MODE | SDRAM_MODE_NORMAL);
        EXTRA_DELAY
        
        /* 10 DDR Receive FIFO RE-Sync */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_10);
-#endif
+       RAM_DEBUG_MESSAGE("Ram Enable 10\r\n");
        RAM_RESET_DDR_PTR(ctrl);
        EXTRA_DELAY
        
        /* 11 normal operation */
-#if DEBUG_RAM_CONFIG 
-       print_debug(ram_enable_11);
-#endif
-       RAM_NORMAL(ctrl);
-
+       RAM_DEBUG_MESSAGE("Ram Enable 11\r\n");
+       do_ram_command(ctrl, RAM_COMMAND_NORMAL, 0);
        EXTRA_DELAY
-        /* Finally enable refresh */
-        ENABLE_REFRESH(ctrl);
 
-       //SPECIAL_FINISHUP();
+       // Reconfigure the row boundaries and Top of Low Memory
+       // to match the true size of the DIMMs
+       configure_e7501_ram_addresses(ctrl, dimm_mask);
+
+    /* Finally enable refresh */
+       dram_controller_mode = pci_read_config32(ctrl->d0, DRC);
+       dram_controller_mode |= (1 << 29);
+       pci_write_config32(ctrl->d0, DRC, dram_controller_mode);
        EXTRA_DELAY
-       dram_finish(ctrl);
 
+       initialize_ecc(ctrl);
+
+       dram_controller_mode = pci_read_config32(ctrl->d0, DRC); /* FCS_EN */
+       dram_controller_mode |= (1<<17);                // NOTE: undocumented reserved bit
+       pci_write_config32(ctrl->d0, DRC, dram_controller_mode);
+
+       RAM_DEBUG_MESSAGE("Northbridge following SDRAM init:\r\n");
+       DUMPNORTH();
+
+//     verify_ram();
+}
+
+//----------------------------------------------------------------------------------
+// Function:           sdram_set_spd_registers
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+// Return Value:       None
+// Description:        Configure SDRAM controller parameters that depend on 
+//                                     characteristics of the DIMMs installed in the system. These 
+//                                     characteristics are read from the DIMMs via the standard Serial 
+//                                     Presence Detect (SPD) interface.
+//
+static void sdram_set_spd_registers(const struct mem_controller *ctrl) 
+{
+       uint8_t dimm_mask;
+
+       RAM_DEBUG_MESSAGE("Reading SPD data...\r\n");
+
+   //activate_spd_rom(ctrl);   Not necessary for this chipset
+
+    dimm_mask = spd_get_supported_dimms(ctrl);
+
+       if (dimm_mask == 0) {
+               print_debug("No usable memory for this controller\r\n");
+    } else {
+
+               enable_e7501_clocks(ctrl, dimm_mask);
+
+               RAM_DEBUG_MESSAGE("setting based on SPD data...\r\n");
+
+               configure_e7501_row_attributes(ctrl, dimm_mask);
+               configure_e7501_dram_controller_mode(ctrl, dimm_mask);
+               configure_e7501_cas_latency(ctrl, dimm_mask);
+               RAM_RESET_DDR_PTR(ctrl);
+
+               configure_e7501_dram_timing(ctrl, dimm_mask);
+               DO_DELAY
+               RAM_DEBUG_MESSAGE("done\r\n");
+       }
+
+       // NOTE: configure_e7501_ram_addresses() is NOT called here.
+       //               We want to keep the default 64 MB/row mapping until sdram_enable() is called, 
+       //               even though the default mapping is almost certainly incorrect.
+       //               The default mapping makes it easy to initialize all of the DIMMs
+       //               even if the total system memory is > 4 GB.
+       //
+       //               Save the dimm_mask for when sdram_enable is called, so it can call
+       //               configure_e7501_ram_addresses() without having to regenerate the bitmask
+       //               of usable DIMMs.
+       pci_write_config16(ctrl->d0, SKPD, dimm_mask);
+}
+
+//----------------------------------------------------------------------------------
+// Function:           sdram_set_registers
+// Parameters:         ctrl - PCI addresses of memory controller functions, and
+//                                             SMBus addresses of DIMM slots on the mainboard
+// Return Value:       None
+// Description:        Do basic ram setup that does NOT depend on serial presence detect 
+//                                     information (i.e. independent of DIMM specifics).
+//
+static void sdram_set_registers(const struct mem_controller *ctrl)
+{
+       RAM_DEBUG_MESSAGE("Northbridge prior to SDRAM init:\r\n");
+       DUMPNORTH();
+
+       ram_set_rcomp_regs(ctrl);
+    ram_set_d0f0_regs(ctrl);
 }
 
+/*^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^*/
+/*                                                                     PUBLIC INTERFACE                                                          */
+/**********************************************************************************/
\ No newline at end of file