NEC Express5800 A2040b Configuration Manual page 55

CONFIGURATION GUIDE
2.4 Memory Rank Sparing
"Memory Rank Sparing" is the feature to keep operation; with having one of two memory ranks in one memory
channel as a spare, when detecting errors at memory rank in operation, automatically switching to spare rank.
To use this feature, need to order memory set including 4 DIMMs per set
Memory Rank Sparing for each Memory Configuration Mode:
Independent Mode: One of two memory rank in each memory channel is assigned as a spare memory rank
Lockstep Mode: Either a memory pair on CH0 and CH1 OR a memory pair on CH02 and CH03 is assigned
as a spare memory rank.
NOTE:

Cannot mix RDIMM and LRDIMM in a server

When using Memory Rank Sparing, the available memory capacity reduces by the capacity of spare
memory rank:

Available Memory Capacity:

Lockstep Mode + Memory Rank Sparing 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 Rank Sparing
NEC Corporation
–
NEC Express5800/A2040b, A2020b, A2010b, A1040b
1/2 of physical memory (8GB RDIMM)
3/4 of physical memory (16GB RDIMM)
7/8 of physical memory (32GB LRDIMM)
3/4 of physical memory (64GB LRDIMM)
Revision 7.0 – December 2014
55