[wscott]

The important thing to understand about why AVX512 is a big deal is not the width. AVX512 adds new instructions and new instruction encodings. They doubled the number of registers (16->32), and added mask registers that allow you to remove special cases at the end of loops when the array is not a multiple of the vector width. And there is piles for new permutation operations and integer operations that allow it to be useful in more cases.

The part Intel struggles with is that in many places if they had the 256-bit max width but all the new operations then they could build a machine that is faster than the 512-bit version. (assuming the same code was written for both vector widths) The reason is the ALUs could be faster and you could have more of them.