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Server Gurus Discussions

Journeyman III

AMD Epyc (Zen 2) disable HW Prefetch L2

Hello everyone!!.

I wan to disable all hardware prefetching on an AMD Epyc 7702P (Zen 2 / Rome). I don't find anything related in the official tech docs (Processor Programming Reference 17H and Manuals).

However, according to BKDG document for 15h. I have managed to disable the L1 prefetch by writing 1 on bit 13 on MSRC001_1022 (the L1-dcache-prefetches hardware counter gives 0). But the L2 Prefetcher Hits/Miss in L3 hardware counter doesn't change, so I assume that L2 Prefetch is on.

Is there any way to disable L2 prefetch?

In the BKDG document I read about the D18F2x11C. Is this a possibility? If that's the case, how can I do it?


2 Replies

Hello agusnt‌,

You should be able to go into your system BIOS and disable both L1 and L2 prefetchers.  The option is present in most platforms that I've seen.


Disabling L1 and L2 caches will slow the performance of any modern processor dramatically. Given the layered approach has been developed for decades its wiser to use what is available for any workload.

AMD does not have the security problems that Intel's hyperthreading was identified with recently. Intel had to completely redesign their CPU logic.