diff --git a/src/include/spd.h b/src/include/spd.h
index 5fb6468..6703ef2 100644
--- a/src/include/spd.h
+++ b/src/include/spd.h
@@ -1,8 +1,8 @@
 /*
- * spd.h: Definitions for Serial Presence Detect (SPD) data
- *		  stored on SDRAM modules
+ * This file is part of the LinuxBIOS project.
  *
  * Copyright (C) 2005 Digital Design Corporation
+ * Copyright (C) 2006 Uwe Hermann <uwe@hermann-uwe.de>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -16,66 +16,117 @@
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  */
 
-#ifndef __SPD_H_DEFINED
-#define __SPD_H_DEFINED
+/*
+ * Serial Presence Detect (SPD) data stored on SDRAM modules.
+ *
+ * Datasheet:
+ *   - Name: PC SDRAM Serial Presence Detect (SPD) Specification
+ *           Revision 1.2A, December, 1997
+ *   - PDF: http://www.intel.com/design/chipsets/memory/spdsd12a.pdf
+ *
+ * Datasheet (alternative):
+ *   - Name: SERIAL PRESENCE DETECT STANDARD, General Standard
+ *           JEDEC Standard No. 21-C
+ *   - PDF: http://www.jedec.org/download/search/4_01_02_00R9.PDF
+ */
 
-// Byte numbers
-#define SPD_MEMORY_TYPE							 2
-#define SPD_NUM_ROWS							 3
-#define SPD_NUM_COLUMNS							 4
-#define SPD_NUM_DIMM_BANKS						 5
-#define SPD_MODULE_DATA_WIDTH_LSB				 6
-#define SPD_MODULE_DATA_WIDTH_MSB				 7
-#define SPD_MODULE_VOLTAGE						 8
-#define SPD_MIN_CYCLE_TIME_AT_CAS_MAX			 9
-#define SPD_DIMM_CONFIG_TYPE					11
-#define	SPD_REFRESH								12
-#define SPD_PRIMARY_DRAM_WIDTH					13
-#define SPD_SUPPORTED_BURST_LENGTHS				16
-#define SPD_NUM_BANKS_PER_DRAM					17
-#define SPD_ACCEPTABLE_CAS_LATENCIES			18
-#define SPD_MODULE_ATTRIBUTES					21
-#define SPD_MIN_CYCLE_TIME_AT_CAS_REDUCED_05	23
-#define SPD_MIN_CYCLE_TIME_AT_CAS_REDUCED_10	25
-#define SPD_MIN_ROW_PRECHARGE_TIME				27
-#define SPD_MIN_RAS_TO_CAS_DELAY				29
-#define SPD_MIN_ACTIVE_TO_PRECHARGE_DELAY		30
-#define SPD_ADDRESS_CMD_HOLD					33
+#ifndef _SPD_H_
+#define _SPD_H_
 
+/* Byte numbers. */
+#define SPD_NUM_MANUFACTURER_BYTES          0  /* Number of bytes used by module manufacturer */
+#define SPD_TOTAL_SPD_MEMORY_SIZE           1  /* Total SPD memory size */
+#define SPD_MEMORY_TYPE                     2  /* (Fundamental) memory type */
+#define SPD_NUM_ROWS                        3  /* Number of row address bits */
+#define SPD_NUM_COLUMNS                     4  /* Number of column address bits */
+#define SPD_NUM_DIMM_BANKS                  5  /* Number of module rows (banks) */
+#define SPD_MODULE_DATA_WIDTH_LSB           6  /* Module data width (LSB) */
+#define SPD_MODULE_DATA_WIDTH_MSB           7  /* Module data width (MSB) */
+#define SPD_MODULE_VOLTAGE                  8  /* Module interface signal levels */
+#define SPD_MIN_CYCLE_TIME_AT_CAS_MAX       9  /* SDRAM cycle time (highest CAS latency), RAS access time (tRAC) */
+#define SPD_ACCESS_TIME_FROM_CLOCK          10 /* SDRAM access time from clock (highest CAS latency), CAS access time (Tac, tCAC) */
+#define SPD_DIMM_CONFIG_TYPE                11 /* Module configuration type */
+#define SPD_REFRESH                         12 /* Refresh rate/type */
+#define SPD_PRIMARY_SDRAM_WIDTH             13 /* SDRAM width (primary SDRAM) */
+#define SPD_ERROR_CHECKING_SDRAM_WIDTH      14 /* Error checking SDRAM (data) width */
+#define SPD_MIN_CLOCK_DELAY_B2B_RAND_COLUMN 15 /* SDRAM device attributes, minimum clock delay for back to back random column */
+#define SPD_SUPPORTED_BURST_LENGTHS         16 /* SDRAM device attributes, burst lengths supported */
+#define SPD_NUM_BANKS_PER_SDRAM             17 /* SDRAM device attributes, number of banks on SDRAM device */
+#define SPD_ACCEPTABLE_CAS_LATENCIES        18 /* SDRAM device attributes, CAS latency */
+#define SPD_CS_LATENCY                      19 /* SDRAM device attributes, CS latency */
+#define SPD_WE_LATENCY                      20 /* SDRAM device attributes, WE latency */
+#define SPD_MODULE_ATTRIBUTES               21 /* SDRAM module attributes */
+#define SPD_DEVICE_ATTRIBUTES_GENERAL       22 /* SDRAM device attributes, general */
+#define SPD_SDRAM_CYCLE_TIME_2ND            23 /* SDRAM cycle time (2nd highest CAS latency) */
+#define SPD_ACCESS_TIME_FROM_CLOCK_2ND      24 /* SDRAM access from clock (2nd highest CAS latency) */
+#define SPD_SDRAM_CYCLE_TIME_3RD            25 /* SDRAM cycle time (3rd highest CAS latency) */
+#define SPD_ACCESS_TIME_FROM_CLOCK_3RD      26 /* SDRAM access from clock (3rd highest CAS latency) */
+#define SPD_MIN_ROW_PRECHARGE_TIME          27 /* Minimum row precharge time (Trp) */
+#define SPD_MIN_ROWACTIVE_TO_ROWACTIVE      28 /* Minimum row active to row active (Trrd) */
+#define SPD_MIN_RAS_TO_CAS_DELAY            29 /* Minimum RAS to CAS delay (Trcd) */
+#define SPD_MIN_ACTIVE_TO_PRECHARGE_DELAY   30 /* Minimum RAS pulse width (Tras) */
+#define SPD_DENSITY_OF_EACH_ROW_ON_MODULE   31 /* Density of each row on module */
+#define SPD_CMD_SIGNAL_INPUT_SETUP_TIME     32 /* Command and address signal input setup time */
+#define SPD_CMD_SIGNAL_INPUT_HOLD_TIME      33 /* Command and address signal input hold time */
+#define SPD_DATA_SIGNAL_INPUT_SETUP_TIME    34 /* Data signal input setup time */
+#define SPD_DATA_SIGNAL_INPUT_HOLD_TIME     35 /* Data signal input hold time */
+#define SPD_SPD_DATA_REVISION_CODE          62 /* SPD data revision code */
+#define SPD_CHECKSUM_FOR_BYTES_0_TO_62      63 /* Checksum for bytes 0-62 */
+#define SPD_MANUFACTURER_JEDEC_ID_CODE      64 /* Manufacturer's JEDEC ID code, per EIA/JEP106 (bytes 64-71) */
+#define SPD_MANUFACTURING_LOCATION          72 /* Manufacturing location */
+#define SPD_MANUFACTURER_PART_NUMBER        73 /* Manufacturer's part number, in 6-bit ASCII (bytes 73-90) */
+#define SPD_REVISION_CODE                   91 /* Revision code (bytes 91-92) */
+#define SPD_MANUFACTURING_DATE              93 /* Manufacturing date (byte 93: year, byte 94: week) */
+#define SPD_ASSEMBLY_SERIAL_NUMBER          95 /* Assembly serial number (bytes 95-98) */
+#define SPD_MANUFACTURER_SPECIFIC_DATA      99 /* Manufacturer specific data (bytes 99-125) */
+#define SPD_INTEL_SPEC_FOR_FREQUENCY       126 /* Intel specification for frequency */
+#define SPD_INTEL_SPEC_100_MHZ             127 /* Intel specification details for 100MHz support */
 
-// SPD_MEMORY_TYPE values
-#define MEMORY_TYPE_SDRAM_DDR	7
+/* SPD_MEMORY_TYPE values. */
+#define SPD_MEMORY_TYPE_FPM_DRAM         1
+#define SPD_MEMORY_TYPE_EDO              2
+#define SPD_MEMORY_TYPE_PIPELINED_NIBBLE 3
+#define SPD_MEMORY_TYPE_SDRAM            4
+#define SPD_MEMORY_TYPE_MULTIPLEXED_ROM  5
+#define SPD_MEMORY_TYPE_SGRAM_DDR        6
+#define SPD_MEMORY_TYPE_SDRAM_DDR        7
+#define SPD_MEMORY_TYPE_SDRAM_DDR2       8
 
-// SPD_MODULE_VOLTAGE values
-#define SPD_VOLTAGE_SSTL2		4
+/* SPD_MODULE_VOLTAGE values. */
+#define SPD_VOLTAGE_TTL                  0 /* 5.0 Volt/TTL */
+#define SPD_VOLTAGE_LVTTL                1 /* LVTTL */
+#define SPD_VOLTAGE_HSTL                 2 /* HSTL 1.5 */
+#define SPD_VOLTAGE_SSTL3                3 /* SSTL 3.3 */
+#define SPD_VOLTAGE_SSTL2                4 /* SSTL 2.5 */
 
-// SPD_DIMM_CONFIG_TYPE values
-#define ERROR_SCHEME_NONE		0
-#define ERROR_SCHEME_PARITY		1
-#define ERROR_SCHEME_ECC		2
+/* SPD_DIMM_CONFIG_TYPE values. */
+#define ERROR_SCHEME_NONE                0
+#define ERROR_SCHEME_PARITY              1
+#define ERROR_SCHEME_ECC                 2
 
-// SPD_ACCEPTABLE_CAS_LATENCIES values
-#define SPD_CAS_LATENCY_1_0		0x01
-#define SPD_CAS_LATENCY_1_5		0x02
-#define SPD_CAS_LATENCY_2_0		0x04
-#define SPD_CAS_LATENCY_2_5		0x08
-#define SPD_CAS_LATENCY_3_0		0x10
-#define SPD_CAS_LATENCY_3_5		0x20
-#define SPD_CAS_LATENCY_4_0		0x40
+/* SPD_ACCEPTABLE_CAS_LATENCIES values. */
+// TODO: Check values.
+#define SPD_CAS_LATENCY_1_0              0x01
+#define SPD_CAS_LATENCY_1_5              0x02
+#define SPD_CAS_LATENCY_2_0              0x04
+#define SPD_CAS_LATENCY_2_5              0x08
+#define SPD_CAS_LATENCY_3_0              0x10
+#define SPD_CAS_LATENCY_3_5              0x20
+#define SPD_CAS_LATENCY_4_0              0x40
 
-// SPD_SUPPORTED_BURST_LENGTHS values
-#define SPD_BURST_LENGTH_1		1
-#define SPD_BURST_LENGTH_2		2
-#define SPD_BURST_LENGTH_4		4
-#define SPD_BURST_LENGTH_8		8
-#define SPD_BURST_LENGTH_PAGE	(1<<7)
+/* SPD_SUPPORTED_BURST_LENGTHS values. */
+#define SPD_BURST_LENGTH_1               1
+#define SPD_BURST_LENGTH_2               2
+#define SPD_BURST_LENGTH_4               4
+#define SPD_BURST_LENGTH_8               8
+#define SPD_BURST_LENGTH_PAGE            (1 << 7)
 
+/* SPD_MODULE_ATTRIBUTES values. */
+#define MODULE_BUFFERED                  1
+#define MODULE_REGISTERED                2
 
-// SPD_MODULE_ATTRIBUTES values
-#define MODULE_BUFFERED			1
-#define MODULE_REGISTERED		2
+#endif /* _SPD_H_ */
 
-#endif 	// __SPD_H_DEFINED