I am trying to wrap my head around how Multi-CPU systems score on CPUmark, and under what conditions CPUmark is a useful metric for the kinds of computations I do. As has been discussed before (https://www.passmark.com/forum/pc-ha...ame-cpu-scores), the speedup from having two CPUs is often in the neighborhood of ~1.3 times the mark for a single CPU. We would of course expect something less than 2X, but the scores are still way below what I would intuitively expect. Nowhere is this more evident than the EPYC 7742, which has a single CPU score of 48062 and a dual score of 55574, a measly 15% increase from adding a whole 64 core flagship CPU.
It feels like adding cores to a single processor scales much more like linear. Take for example the Xeon Gold 6140 and 5218. Adding cores here looks much closer to linear (23964/1 / (20622/16) ~=1.
So I guess my question is: Where is the bottleneck and how does it relate to adding cores/cpus? Reading the methodology, it appears that tests are run in fully independent processes that don't share any information. No network of hard drives are hit by the benchmarks. The only shared resource would be RAM, correct? Intuitively, it seems like multi-cpus should scale even better than adding cores due to additional cache and heat dissipation.
It feels like adding cores to a single processor scales much more like linear. Take for example the Xeon Gold 6140 and 5218. Adding cores here looks much closer to linear (23964/1 / (20622/16) ~=1.
So I guess my question is: Where is the bottleneck and how does it relate to adding cores/cpus? Reading the methodology, it appears that tests are run in fully independent processes that don't share any information. No network of hard drives are hit by the benchmarks. The only shared resource would be RAM, correct? Intuitively, it seems like multi-cpus should scale even better than adding cores due to additional cache and heat dissipation.
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