Here is Knuth introducing the MMIX instruction MXOR, which Intel later defined on vector registers under the name vgf2p8affineqb.

https://www.youtube.com/watch?v=r_pPF5npnio&t=3300 (55:00)

"This is an instruction that doesn't exist in any computer right now, so why should I put it in a machine, if it's supposed to be realistic? Well, it's because it's ahead of time."