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Running this code on an "on-prem" AMD EPYC 9454P with 12 x 64 GB DIMMs:

  1 37.4
  2 73.3
  3 107.3
  4 141.4
  5 171.6
  6 199.5
  7 226.0
  8 251.1
  9 235.4
  10 243.0
  11 264.5
  12 281.9
  13 303.7
  14 323.0
  15 339.6
  16 354.4
  17 299.0
  18 286.3
  19 300.9
  20 310.6
  21 325.7
  22 339.2
  23 352.6
  24 364.3
  25 305.8
  26 309.0
  27 319.6
  28 326.5
  29 335.4
  30 345.5
  31 356.7
  32 364.9
And then it settles around there.



What are the units? MB/s, GB/s


looks like GB/s


So around 3x of what AWS has? I guess this is more about what motherboard they have, and not an on-prem vs cloud difference.


1.5 times greater speed comes from 768-bit vs. 512-bit width of the memory interface.

Another 1.5 times greater speed comes from DDR5-4800 vs. DDR4-3200.

The rest may be from virtualization and other overheads.


Number of DIMM is important, I know the standard BOM at my company has way more memory that we use just to have more bandwidth.


Bandwidth increases nearly linearly with adding dimms until you get to 1 dimm per memory channel. After that there's very small improvements related to more open pages. More open pages doesn't help with pure bandwidth benchmarks though.




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