Can't argue with 1. For 2 it's still an instruction set separate from uops so you might not be as sensitive to changes you still get a level of indirection. For

Can't argue with 1. For 2 it's still an instruction set separate from uops so you might not be as sensitive to changes you still get a level of indirection. For 3 .. it depends. You might gain in power if you use the newer one more and you might as well make the older one simpler to achieve 90% of speed maybe. But maybe the decoding of instructions that counts is not that expensive compared to OOO branch predictors and 512 bits ALUs