populating RAM in 4-node Gigabyte EPYC server

[Phil Marsh]

Hi,
I'm in the process of populating the RAM of a Gigabyte H261-Z61 2U
four-node server which has two EPYC 7551's/node (Naples).
This will be used to solve FDTD electromagnetic calculations which generate
huge memory traffic and whose speed/performance depends largely on RAM
performance/speed.
I suspect that each CPU needs to have all the same RAM speeds (e.g.
2400MHz), same RAM sizes and same RAM rank number (e.g. rank 1 or 2). What
do you think? Do I need to match the rank numbers too?
I know I need to match the RAM speeds for the 16 slots of a single node
to maximize RAM performance.
While the machines will work with mismatched RAM, I'm sure the performance
will be degraded due to interleaving being shut off. These are EPYC 7551
(two CPUs/node) with eight channel RAM and one RAM module per channel - 8
RAM slots. I think I can get away with different RAM sizes and rank numbers
/ node provided I populate each node with the same frequency RAM and each
CPU with the same size and rank number, but still researching this. I think
I could have mismatched rank (1 or 2) and mismatched RAM sizes within a
node so long as they are matched within a CPU?
Please kindly give your advice.
Thanks,
Phil
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