Memory Subsystem Architecture; Single-, Dual-, And Quad-Rank Dimms; Dimm Identification - HP ProLiant BL490c - G6 Server User Manual

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Single- and dual-rank PC3-10600 (DDR-1333) DIMMs operating at 1333 and 1066 MHz
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Quad-rank PC3-8500 (DDR-1067) DIMMs operating at 1066 MHz
Depending on the processor model, the number of DIMMs installed, and whether UDIMMs or RDIMMs
are installed, the memory clock speed may be reduced to 1066 or 800 MHz. For more information on
the effect of DIMM slot population, see "General DIMM slot population guidelines (on page 25)."

Memory subsystem architecture

The memory subsystem in this server blade is divided into channels. Each processor supports three
channels, and each channel supports three DIMM slots, as shown in the following table.
Channel
1
2
3
This multi-channel architecture provides enhanced performance in Advanced ECC mode. This architecture
also enables the Mirrored Memory and Lockstep memory modes. This server blade supports both
Registered PC3 DIMMSs (RDIMMs) and Unbuffered DIMMs (UDIMMs).
DIMM slots in this server are identified by number and by letter. Letters identify the slots to populate for
specific AMP modes. Slot numbers are reported by ROM messages during boot and for error reporting.

Single-, dual-, and quad-rank DIMMs

To understand and configure memory protection modes properly, an understanding of single-, dual-, and
quad-rank DIMMs 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 server blade 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 2-GB single-rank DIMMs, a dual-rank DIMM would be 4-
GB, and a quad-rank DIMM would be 8-GB.

DIMM identification

IMPORTANT:
mix these two types causes the server to halt during BIOS initialization.
Slot
G
D
A
H
E
B
I
F
C
This server blade does not support mixing RDIMMs and UDIMMs. Attempting to
Slot number
1
2
3
4
5
6
7
8
9
Hardware options installation 22