@robpike Re (2), a few years back I stumbled upon this 2002 paper: https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=0366820530b662bd1c3a912720ce23795862d1ba, which describes a stack machine microarchitecture with out-of-order execution, achieving ILP comparable to register machines ([*] in mathematical modeling, didn't make it to silicon afaict).This was in the heyday of getting java to run on the metal, but the paper's conclusion points to how things actually panned out: you can have any microarchitecture you want, as long as the frontend's x86_64.