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It doesn't solve all of it however. If your program has more than "$number_of_cores / 2" threads, you'll cross the CCX boundary at some point(s). On Zen 2, that instead changes to "$number_of_cores / 4" (CCX boundary) or "$number_of_cores / 2" (chiplet boundary).

Inter-CCX communication requires hopping over the Infinity Fabric bus, which (in case of Zen 1, no newer benchmarks) increases thread latency from ~45us to ~131us. I'm sure it was reduced in Zen+ and is probably closer to 100us by now. However, I'm not sure if inter-chiplet communication will be the same (e.g.: has its own IF bus) or worse (IO chip overhead).

Hopefully someone runs the same inter-thread communication benchmarks on Zen 2.



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