Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!rutgers!apple!oliveb!pyramid!prls!mips!mash From: mash@mips.COM (John Mashey) Newsgroups: comp.arch Subject: Re: RISC as a "technology window"? Message-ID: <15695@winchester.mips.COM> Date: 22 Mar 89 07:38:11 GMT References: <1552@vicom.COM> <15690@cup.portal.com> <1562@vicom.COM> <15702@clover.ICO.ISC.COM> <27681@apple.Apple.COM> Reply-To: mash@mips.COM (John Mashey) Organization: MIPS Computer Systems, Sunnyvale, CA Lines: 41 In article <27681@apple.Apple.COM> jrg@Apple.COM (John R. Galloway) writes: >In article <15702@clover.ICO.ISC.COM>, rcd@ico.ISC.COM (Dick Dunn) writes: >> In article <37196@bbn.COM>, slackey@bbn.com (Stan Lackey) writes: >> > RISC is indeed a technology window, driven largely by the amount of >> > stuff you can fit in a chip... >> >> OK, fair 'nuff. As soon as we can put an unlimited amount of stuff on a >> chip (and do it without increasing delays or other limitations), we'll be >> beyond that technology window, I guess... .... >Well actually only while the "extra" space is less than a full cpu, as soon >as it is we will just get multiple cpus on a chip and they may well still be >RISC oriented. In fact with the extra cost of packaging, I could imagine >that as soon as this point is approached all extras will be stripped off to >squeeze the extra one in. Can anyone tell us where to get some of this kind of silicon? (the kind you can put unlimited stuff on :-) we want some. I'm sure Intel, Moto, Sun would like some also. Seriously, I doubt that anyone has silicon to burn. In particular, the faster the chips get, the more it hurts you to go off chip. Bigger on-chip caches [I, D, or TLB] keep you on-chip more, and are therefore good. With more hardware, you can make integer multiplies go faster, make FP go faster, and maybe put in some multiple FP units, a la CDC 6600s [and these things chew up area]. Note that Intel, with a million transistors, said the space budget didn't leave room for an IEEE divide..... (Compcon paper). I suspect it will be some time before people replicate the CPUs on a chip, just because there's nothing else to do with the silicon. a) It's hard to get enough bandwidth in and out of these chips, i.e., I/Os cost money. b) If you replicate CPUs on a chip, it would like more bandwidth. c) If you double the size of a giant-monster-chip, its yield might get a lot worse... -- -john mashey DISCLAIMER: UUCP: {ames,decwrl,prls,pyramid}!mips!mash OR mash@mips.com DDD: 408-991-0253 or 408-720-1700, x253 USPS: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086