Memory Subsystem - Compaq Evo D500 Technical Reference Manual

3.3

MEMORY SUBSYSTEM

The system boards for these systems provide three 168-pin SDRAM DIMM sockets that
accommodate single- or double-sided DIMMs and can handle a maximum of 512 megabytes of
SDRAM. These systems support (and are shipped with) PC133 SDRAM for system memory,
providing a maximum possible throughput of 1 GB/s.
NOTE: For 133-MHz SDRAM operation to occur, all of the following criteria must
be met:
1. The processor's FSB must operate at 133-MHz.
2. All installed DIMMs must be PC133-compliant.
3. The total number of DIMM "sides" is no greater than four:
a.
b. Three single-sided DIMMs or
c.
The BIOS will automatically switch the SDRAM speed to 100 MHz if all of the
above criteria are not met.
If using memory modules from third party suppliers the following DIMM type is recommended:
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.
One double-sided and two single-sided DIMMs or
Two double-sided DIMMs (with remaining socket empty).
Unbuffered 133-MHz SDRAM (PC133)
CAS latency (CL) 2 or 3
Data access time (clock-to-data out) of < 9.0 ns
Featuring Intel Celeron and Pentium III Processors
Fifth Edition - March 2002
Technical Reference Guide
Compaq Deskpro and Evo Personal Computers 3-5