Operator asked why not move all 768 GB across. It does not fit the
board's shape: the R640 has 24 slots at 6 channels/socket x 2 DPC, the
R750xa has 16 at 8 channels/socket x 1 DPC.
768 GB is either 24x 32 GB (more DIMMs than slots) or 12x 64 GB (fits,
but populates 6 of 8 channels per socket and gives up ~25% of memory
bandwidth). The board wants 16 identical DIMMs. So the targets are
512 GB if they are 32s, or 1 TB if they are 64s — taking 12 from one
spare and 4 from the other. In the 64 GB case the answer beats the
question.
Also recorded: beyond ~512 GB the return is marginal for this workload,
so take 1 TB because it is free rather than because it is needed; 64 GB
LRDIMMs run ~50 W hotter in a chassis whose high-performance fans are
unaccounted for on the invoice; and DIMM slot count now needs to be on
the iDRAC pull, since the 16-slot figure is inferred from the factory
CSV and is load-bearing for a 512-vs-1024 decision.
Memory-only; no version bump per the SemVer SKIP list.
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