Memory Subsystem - HP Compaq dc7800 Series Technical Reference Manual

Processor/Memory Subsystem

3.3 Memory Subsystem

All models support non-ECC PC2-5300 and PC2-6400 DDR2 memory. The USDT form factor
supports up to four gigabytes of memory while the SFF and CMT form factors support up to
eight gigabytes of memory.
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The DDR SDRAM "PCxxxx" reference designates bus bandwidth (i.e., a PC2-5300 module can,
operating at a 667-MHz effective speed, provide a throughput of 5300 MBps (8 bytes ×
667MHz)). Memory speed types may be mixed within a system, although the system BIOS will
set the memory controller to work at speed of the slowest memory module.
The USDT system board provides two SODIMM sockets and the SFF and CMT system boards
provide four DIMM sockets
■
XMM1, channel A (black)
■
XMM2, channel A (white, not present in USDT form factor)
■
XMM3, channel B (white)
■
XMM4, channel B (white, not present in USDT form factor)
Memory modules do not need to be installed in pairs although installation of pairs (especially
matched sets) provides the best performance. The XMM1 socket must be populated for proper
support of Intel Advanced Management Technology (AMT). The BIOS will detect the module
population and set the system accordingly as follows:
■
Single-channel mode - memory installed for one channel only
■
Dual-channel asymetric mode - memory installed for both channels but of unequal channel
capacities.
■
Dual-channel interleaved mode (recommended) - memory installed for both channels and
offering equal channel capacities, proving the highest performance.
These systems support memory modules with the following parameters:
■
Unbuffered, compatible with SPD rev. 1.0
■
512-Mb, and 1-Gb memory technologies for x8 and x16 devices
■
CAS latency (CL) of 5 or 6 (depending on memory speed)
■
Single or double-sided
■
Non-ECC memory only
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
HP-added features such as part number and serial number.
If BIOS detects an unsupported memory module, a "memory incompatible" message will be
displayed and the system will halt. These systems are shipped with non-ECC modules only.
An installed mix of memory module types is acceptable but operation will be constrained to the
level of the module with the lowest (slowest) performance.
If an incompatible memory module 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.
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