> The issue with AVX512 is not (just) that you need a very wide vector unit, but mostly that you need an incredibly large register file
Not necessarily, you need to behave as if you had that many registers, but IMO it would be way better if the E cores had supported avx512, but half of the registers actually didn't exist and just were in the L2 cache.
Also Zen4C has AVX512 support while being only ~35% bigger than Gracemont (although TSMC node advantage means you should possibly add another 10% or so). This isn't really a fair comparison because Zen4c is a very differently optimized core than Intel's E cores, but I do think it shows that AVX-512 can be implemented with a reasonable footprint.
Or if Intel really didn't want to do that, they needed to get AVX-10 ready for 2020 rather than going back and forth on it fore ~8 years.
Not necessarily, you need to behave as if you had that many registers, but IMO it would be way better if the E cores had supported avx512, but half of the registers actually didn't exist and just were in the L2 cache.