Hardware options installation 51
Qualified memory is performance-tuned for ProLiant and BladeSystem servers and provides future
enhanced support through Active Health and manageability software.
Memory subsystem architecture
The memory subsystem in this server is divided into channels. Each processor supports four channels,
and each channel supports one DIMM slot.
Channel Population order Slot number
1
2
DIMM slots are identified by number and by letter. Letters identify the population order. Slot numbers are
reported by ROM messages during boot and are used for error reporting. For the DIMM slot locations, see
"DIMM slot locations."
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 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.
LRDIMMs are labeled as quad-rank DIMMs. There are four ranks of DRAM on the DIMM, but the
LRDIMM buffer creates an abstraction that allows the DIMM to appear as a dual-rank DIMM to the
system. The LRDIMM buffer isolates the electrical loading of the DRAM from the system to allow for faster
operation. This allows higher memory operating speed compared to quad-rank RDIMMs.
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