NEC Express5800 A2040b Configuration Manual page 54

CONFIGURATION GUIDE
2-3. Memory Mirroring
"Memory Mirroring" provide redundancy by writing the same data into 2x memory among different memory
buffers on a Memory Riser Card. To use this feature, need to order memory set including 4 DIMMs per set
Memory Mirroring for each Memory Configuration Mode:
Independent Mode: Mirroring between CH0 and CH2, CH1 and CH3
Lockstep Mode: Mirroring between memory pair on CH0 and CH1 AND memory pair on CH2 and CH3
NOTE:

Cannot mix RDIMM and LRDIMM in a server

When using Memory Mirroring, the available memory capacity becomes half of physical capacity.

Lockstep Mode + Memory Mirroring is a standard setting at the server delivery. To use Independent
Mode, need to change the mode from BIOS set-up menu.

Cannot use both Memory Mirroring and Memory Rank Sparing at the same time.
For DIMM installation priority/order, (1) to install larger DIMM first, and (2) to install DIMMs to the sockets in
the priority/order shown in the figure below.
DIMM Installation Order for Memory Mirroring
NEC Corporation
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NEC Express5800/A2040b, A2020b, A2010b, A1040b
Revision 7.0 – December 2014
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