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Do both E and P cores handle avx instructions or are some instructions specific to p-cores? In that case, how does a processor with heterogeneous cores deal wit
by alkonaut 5y ago
Do both E and P cores handle avx instructions or are some instructions specific to p-cores? In that case, how does a processor with heterogeneous cores deal with processes (or, how does the OS/driver do it in automatic mode when affinity isn’t guided)?
- avx512 5y agoThe elephant in the room is the classic CPU architecture mistake where you use two different instruction sets on your performance and efficiency cores. There is no way to prevent code with AVX-512 instructions from being executed on an unsupported core. This exact same problem that plagued early ARM big.LITTLE designs that used ARMv8.2 on the performance core but ARM8.0 on the efficiency core, forcing all code to use the more restrictive instruction set and cripple the performance benefits of the “big” cores.
- Iwan-Zotow 5y agoYeah, it killed heterogenic MPI clusters before as well
- BeeOnRope 5y agoThe E and P cores support the same instruction sets (apart from this thing where you could run AVX-512 on the P cores if you disabled the E cores, which is going away).
- PragmaticPulp 5y agoNope! You have to disable the efficiency cores to enable AVX-512. Between that and the relative scarcity of AVX-512 code, this isn’t really a big loss. It wasn’t like it was a free feature.