Technical Reference Guide

3.3MEMORY SUBSYSTEM

These systems support one of two types of memory: single data rate (SDR) SDRAM or double data rate (DDR) SDRAM. The system board determines the type of memory supported:

SDR SDRAM-based system board: Three 168-pin DIMM sockets that accept PC100 or PC133 (PC133 supplied) DIMMs.

DDR SDRAM-based system board: Two 184-pin DIMM sockets that accept PC1600 or PC2100 (PC2100 supplied) DIMMs.

NOTE: The two memory types are not interchangeable within a system. The system board determines memory type.

NOTE: The SDR SDRAM "PCxxx" reference designates bus speed (i.e, a PC133 DIMM is designed for 133 MHz operation). The DDR SDRAM "PCxxxx" reference designates bus bandwidth (i.e., a PC2100 DIMM can, operating at a 266-MHz effective speed, provide a throughput of 2100 MBps (8 bytes × 266 MHz)).

These systems accept DIMMs with the following parameters:

Unbuffered, compatible with SPD rev. 1.0

32-, 64-, 128-, 256-, and 512-Mb memory technology

Single or double-sided

NOTE: Systems that support DDR SDRAM accept either ECC or non-ECC DIMMs, but not both.

The SPD format supported by these systems complies with the JEDEC specification for 128-byte EEPROMs. This system also provides support for 256-byte EEPROMs to include additional Compaq-added features such as part number and serial number. The SPD format as supported in this system (SPD rev. 1) is shown in Table 3-3.

The key SPD bytes that BIOS checks for compatibility are 2, 9, 10, 18, 23, 24, and 126. If BIOS detects EDO or ECC DIMMs a “memory incompatible” message will be displayed and the system will halt. This system is designed for using non-ECC DIMMs only. Refer to chapter 8 for a description of the BIOS procedure of interrogating DIMMs.

An installed mix of DIMM types (PC100 and PC133, CL 2 and CL 3) is acceptable but operation will be constrained to the level of the DIMM with the lowest performance specification.

If an incompatible DIMM is detected the NUM LOCK will blink for a short period of time during POST and an error message may or may not be displayed before the system hangs.

Compaq Evo and Workstation Personal Computer 3-5

Featuring the Intel Pentium 4 Processor

Second Edition - January 2003

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Compaq W4000 manual Memory Subsystem