Why Ryzen's performance is so different: Cache and Compute Complexes

BGL · March 13, 2017, 6:45pm

Probably worth asking one of the mods to combine threads...

PCPer talk about their investigation into RyZen odd performance benchmarks where they found some interesting information CPU

TL;DW: They checked Windows Scheduler and Core numbering to be sure it wasn't mis-numbering the cores and thereby causing issues with latency on memory access, or mis-handling threads causing performance degradation. They found it did not do that, but when the set of 4 cores on one CCX has to communicate with the 4 cores on the other CCX, an extra 100 ns of latency is added to the average of about 40 ns. Windows has no way to know that and it's not intelligent enough to see that is a re-occurring issue and to work around it. Personally, I found those results weird. In most gaming benchmarks, one in particular that was mentioned was for BF1, RyZen tends to have higher lows in terms of FPS than the Intel equivalent. You'd think having some added memory latency between CCXs would make those worse, not better.

I think alot of this is also now in the long-running Ryzen no-BS thread.