Processor/Memory Subsystem

3.3Memory Subsystem

The dx6100 and dc7100 models support PC2700 or PC3200 DDR memory and come standard with PC3200 DIMMs installed. The dx6120 models support PC2-4300 DDR2 memory only.

✎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 (DDR, blue connector; DDR2, white connector), channel A (SFF, ST, MT, and CMT form factors only)

■XMM3 (black connector), channel B (all form factors)

■XMM4 (DDR, blue connector; DDR2, white 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.

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Technical Reference Guide