AVX-512 does not do to micro-op splitting (on intel server class CPU's, it does on some intel consumer cpu's).

Amusing Zen is emulating AVX512 and AVX2 via micro-op splitting and it performs better under some workloads.

The real issue is path propagation delays of 512bits worth of electricity is extremely non-trivial, and costs a shit load of power. Just `mov`'ing to the AVX-512 instructions (initially when AVX-512 is not warm) can stall the CPU for 10,000+ cycles as it tries to power on all those registers.