Comment by lunixbochs

your single core numbers seem way too low for peak throughput on one core, unless you stipulate that all cores are active and contending with each other for bandwidth

e.g. dual channel zen 1 showing 25GB/s on a single core https://stackoverflow.com/a/44948720

I wrote some microbenchmarks for single-threaded memcpy

    zen 2 (8-channel DDR4)
    naive c:
      17GB/s
    non-temporal avx:
      35GB/s

    Xeon-D 1541 (2-channel DDR4, my weakest system, ten years old)
    naive c:
      9GB/s
    non-temporal avx:
      13.5GB/s

    apple silicon tests
    (warm = generate new source buffer, memset(0) output buffer, add memory fence, then run the same copy again)

    m3
    naive c:
      17GB/s cold, 41GB/s warm
    non-temporal neon:
      78GB/s cold+warm

    m3 max 
    naive c:
      25GB/s cold, 65GB/s warm
    non-temporal neon:
      49GB/s cold, 125GB/s warm

    m4 pro
    naive c:
      13.8GB/s cold, 65GB/s warm
    non-temporal neon:
      49GB/s cold, 125GB/s warm

    (I'm not actually sure offhand why asi warm is so much faster than cold - the source buffer is filled with new random data each iteration, I'm using memory fences, and I still see the speedup with 16GB src/dst buffers much larger than cache. x86/linux didn't have any kind of cold/warm test difference. my guess would be that it's something about kernel page accounting and not related to the cpu)

I really don't see how you can claim either a 6GB/s single core limit on x86 or a 20GB/s limit on apple silicon