Huh, seems you are right. I've read about "not really real" AVX-512 implementation in Zen 4, and also saw that on my workload turning on AVX-512 on Zen 4 indeed

Huh, seems you are right. I've read about "not really real" AVX-512 implementation in Zen 4, and also saw that on my workload turning on AVX-512 on Zen 4 indeed gives almost nothing (compared to x2 speedup on Intel). But now that you've written it, I understood that my only test was very specific, full of 32-bit FMAs, and I was comparing Zen 4 with Skylake-X which has 2 FMA units.