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Well, there are some things that the ISA impacts, most notably the translation overhead (modern day x86 "CISC" implementations are really essentially RISC proce
by deepnotderp 9y ago
Well, there are some things that the ISA impacts, most notably the translation overhead (modern day x86 "CISC" implementations are really essentially RISC processors with a translation layer over it). Jim Keller, who's been on both sides estimates that fully developed RISC ISAs should be about ~15-20% more efficient than their x86 counterparts.
- ajross 9y agoThat seems, let's just say awfully generous considering that we're well into the End of Silicon Scaling at this point and no such advantage has been seen yet. But whatever. The point isn't to say you can't design a bad ISA that would have performance impact, but that arguing about ISA as if it were a core driver of processor performance is dumb. Stated less charitably: programmers like us like to argue about ISA because we understand that stuff and want to bike shed about something that makes us feel smart. The real issues with CPU design happen elsewhere, as literally illustrated by the linked presentation!
- phkahler 9y agoDo you have a reference for that Jim Keller estimate? BTW he's at nVidia and they have a solid interest in risc-v ;-)
- deepnotderp 9y agoHe's at Tesla after being at AMD and Apple, I don't think he was ever at nvidia.
- phkahler 9y agowhoops that's right. My dumb. Still interested in the quote.