See this correct comment above: https://news.ycombinator.com/item?id=47061696

AVX512 leading to thermal throttling is a common myth that from what I can tell traces its origins to a blog post about clock throttling on a particular set of low-TDP SKUs from the first generation of Xeon CPUs that supported it (Skylake-X), released over a decade ago: https://blog.cloudflare.com/on-the-dangers-of-intels-frequen...

The results were debated shortly after that by well-known SIMD authors that were unable to duplicate the results: https://lemire.me/blog/2018/08/25/avx-512-throttling-heavy-i...

In practice, this has not been an issue for a long time, if ever; clock frequency scaling for AVX modes has been continually improved in subsequent Intel CPU generations (and even more so in AMD Zen 4/5 once AVX512 support was added).