On linux distros, the package manager downloads different binaries based on your CPU. Skylake would be x86-64-v3, Zen 4 would be x86-64-v4, for example.
And there are different schemes for multiple architectures in the same program, like hwcaps.
And there are different schemes for multiple architectures in the same program, like hwcaps.
Work out what it would cost to compile - say - a terabyte of C code at typical cloud spot prices.
A large VM with 128 cores can compile the 100 MB Linux kernel source tree in about 30 seconds. So… 200 MB/minute or 12 GB/hour. This would take 80 hours for a terabyte.
A 120 core AMD server is about 50c per hour on Azure (Linux spot pricing).
So… about $40 to compile an entire distro. Not exactly breaking the bank.
https://developers.redhat.com/blog/2021/01/05/building-red-h...
There is discussion of a fifth level. Someone in the Intel Clear Linux IRC said a fifth level wasn't "worth it" for Sapphire Rapids because most of the new AVX512 extensions were not autovectorized by compilers, but that a new level would be needed in the future. Perhaps they were thinking of APX, but couldn't disclose it.
We can throw away any hope of v4 being a standard baseline.