There was a longstanding issue where AVX-512 would trigger frequency throttling on a number of Intel CPUs, resulting in a net performance penalty for mixed workloads.
No, there was a longstanding issue of people worrying that it would result in a net performance penalty for mixed workloads. Meanwhile people actually using AVX-512 dealt with that by making sure mixed workloads were batched appropriately and it is usually a big net win even if you don't worry about it.
Ok, but that hasn’t been a problem in a while.
Hasn't been a problem because software corrected for that, or hasn't been a problem because Intel resolved the underlying throttling issues with AVX-512?
Both
It was never really a problem.
It was only useful in a couple of corner cases, but not in general library functions.
Intel could never fix its thermal issues, AMD did.
Yeah, but the mystique still lingers on.
“Longstanding” here means “really only in a single CPU generation (SKX), and even then only if you were dumb and used like 50 AVX-512 instructions in isolation for no reason at all.”