Dimm Ranks; Dimm Identification - HP Synergy 480 Gen9 User Manual

Memory subsystem
channel
1
2
3
4
For the location of the slot numbers, see "DIMM slot locations."
This multi-channel architecture provides enhanced performance in Advanced ECC mode. This architecture
also enables Lockstep and Online Spare Memory modes.
DIMM slots in this server are identified by number and by letter. Letters identify the population order. Slot
numbers indicate the DIMM slot ID for spare replacement.

DIMM ranks

To understand and configure memory protection modes properly, an understanding of DIMM rank is helpful.
Some DIMM configuration requirements are based on these classifications.
A single-rank DIMM has one set of memory chips that is accessed while writing to or reading from the
memory. A dual-rank DIMM is similar to having two single-rank DIMMs on the same module, with only one
rank accessible at a time. A quad-rank DIMM is, effectively, two dual-rank DIMMs on the same module. Only
one rank is accessible at a time. The compute module memory control subsystem selects the proper rank
within the DIMM when writing to or reading from the DIMM.
Dual- and quad-rank DIMMs provide the greatest capacity with the existing memory technology. For example,
if current DRAM technology supports 8-GB single-rank DIMMs, a dual-rank DIMM would be 16 GB, and a
quad-rank DIMM would be 32 GB, and an octal-rank LR DIMM would be 64 GB.
LR DIMMs are labeled as quad- and octal-rank DIMMs. There are four and eight ranks of DRAM on the
DIMM, but the LR DIMM buffer creates an abstraction that allows the DIMM to appear as a logical dual-rank
DIMM to the system. This is called Rank Multiplication. The LR DIMM buffer also isolates the electrical
loading of the DRAM from the system to allow for faster operation. These two changes allow the system to
support up to three LR DIMMs per memory channel, providing for greater memory capacity and higher
memory operating speed compared to quad-rank R DIMMs.

DIMM identification

To determine DIMM characteristics, see the label attached to the DIMM and refer to the following illustration
and table.
34 DIMM ranks
Population order
A E I
B F J
C G K
D H L
Slot number (Processor
1)
12 11 10
9 8 7
1 2 3
4 5 6
Slot number (Processor
2)
1 2 3
4 5 6
12 11 10
9 8 7