> I wonder how much of an x86 chip is dedicated to handling legacy instructions or largely unnecessary instructions. How much saving could be achieved by a radi

> I wonder how much of an x86 chip is dedicated to handling legacy instructions or largely unnecessary instructions. How much saving could be achieved by a radically simpler instruction set (for example no neg/call/ret/push/pop/bcd instructions). It's been a long time since I was in a closely related biz, but back then, the answer was "not much if you want to go fast". Instruction decode isn't a huge deal. Micro-op sequencing isn't a big deal if you're going out of order (and many risc instructions tend to get broken into micro-ops). The number of architectural registers used to be a big thing, but X86_64 is good enough. (I don't know if anyone got around to renaming memory.)