Figure 5-16 DIMM installation rules
5.8.3 DIMM Ranks
Understanding single-rank, dual-rank, and quad-rank DIMMs is helpful for correctly
configuring memory protection modes. Some DIMM configuration requirements are based on
these classifications.
l A single-rank DIMM has one set of memory chips that are accessed while data is written
to or read from the memory.
l A dual-rank DIMM has two single-rank DIMMs on the same module, and only one rank
is accessible at a time.
l A quad-rank DIMM has two dual-rank DIMMs on the same module, and only one rank
is accessible at a time.
The server memory control subsystem selects a proper rank within the DIMM when data is
written to or read from the DIMM.
Dual- and quad-rank DIMMs provide the greatest capacity with the existing memory
technology. For example, if the current DRAM technology supports 8 GB single-rank
DIMMs, a dual-rank DIMM can offer a capacity of 16 GB, and a quad-rank DIMM can offer
a capacity of 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 logical
dual-rank DIMM to the system. The LRDIMM buffer also isolates the electrical loading of
the DRAM from the system to allow for faster operation. These two changes provide a higher
memory operating speed compared with quad-rank RDIMMs.
TaiShan 2280 V2 Server
User Guide
5 Optional Part Installation
Issue 01 (2019-07-01) Copyright © Huawei Technologies Co., Ltd. 99
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