Memory Subsystem - HP Compaq dx6100 Series Technical Reference Manual

Processor/Memory Subsystem

3.3 Memory Subsystem

These systems support PC2700 or PC3200 DDR memory and come standard with PC3200
DIMMs installed.
The DDR SDRAM "PCxxxx" reference designates bus bandwidth (i.e., a PC2700 DIMM can,
operating at a 333-MHz effective speed, provide a throughput of 2700 MBps (8 bytes ×
333MHz)). 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 DIMM.
The system board provides three or four DIMM sockets depending on form factor:
XMM1 (black connector), channel A (all form factors
XMM2 (blue connector), channel A (SFF, ST, MT, and CMT form factors only)
XMM3 (black connector), channel B (all form factors)
XMM4 (blue connector), channel B (all form factors)
DIMMs do not need to be installed in pairs although installation of pairs (an equal DIMM for
each channel) provides the best performance. The BIOS will detect the DIMM population and set
the system accordingly as follows:
Single-channel mode - DIMMs installed for one channel only
Dual-channel asymetric mode - DIMMs installed for both channels but of unequal channel
capacities.
Dual-channel interleaved mode (recommended)- DIMMs installed for both channels and
offering equal channel capacities, proving the highest performance.
These systems require DIMMs with the following parameters:
Unbuffered, compatible with SPD rev. 1.0
256-Mb, 512-Mb, and 1-Gb memory technology
x8 and x16 DDR devices
CAS latency (CL) of 2.5 or 3
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. The SPD format as supported in this
system (SPD rev. 1) is shown in Table 3-1.
If BIOS detects an unsupported DIMM, a "memory incompatible" message will be displayed
and the system will halt. These systems are shipped with non-ECC DIMMs only. Refer to
chapter 8 for a description of the BIOS procedure of interrogating DIMMs.
An installed mix of DIMM types (i.e., PC2700 and PC3200, CL 2 and CL 3) is acceptable but
operation will be constrained to the level of the DIMM with the lowest (slowest) 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.
3-4 361834-001 Technical Reference Guide