Crucial says approximately 3W per 8GB: https://www.crucial.com/support/articles-faq-memory/how-much...

  $ echo '(32 * 2^40) / (8 * 2^30) * 3' | bc
  12288

For what its worth, a significant fraction of that is in the communication interfaces, and not from the ram itself, and there have already been significant process improvements to reduce ram power consumption. A modern 256GB RDIMM draws a heck of a lot less then 50w--I have never measured but based on the thermal solution I would say closer to 5w

I don't see how that could be true. On my server right here with a Xeon Silver 4114 it is measuring the power consumption of the memory at ~75W for 256GB.

Like I said, ram power consumption does not scale linearly with capacity due to the significant overhead from the IO. A single 128GB stick will draw much less than 16x16gb sticks (not sure why you are using 256GB on a 4114, it has 6 memory channels so surely you have 288GB?)

Here is the datasheet for a 128GB dimm from 2017 [1], which shows 3.4A IDD0 (normal operation) on the 1.2V rail at the highest speed of DDR4-2666, and 0.2A on the 2.5V precharge rail for a total of just over 6W. Also worth noting is that is a LRDIMM, which draws more power from the DC rails due to the additional buffering. A normal RDIMM draws a bit less static power.

Compare to a manual for a similar vintage 32GB stick [2], which consumes 2A on the 1.2V rail and 0.1A on the precharge rail for a total of a bit under 3w. One quarter the capacity, but still half of the power draw.

[1] https://www.samsung.com/semiconductor/global.semi/file/resou... [2]https://static6.arrow.com/aropdfconversion/d3b3ce1d78b0ad7d3...

If I could send you back in time to stop this machine's designer from deploying it at scale with some of the channels depopulated, I would! It's an HPE DL360 g10, if you go look at their catalog you'll see that all of the off-the-shelf and BTO memory configs are nonsense.

Thanks for doing the math on the power story. I didn't realize about the scaling.