mash@mips.com (John Mashey) (05/04/91)
In article <8283@uceng.UC.EDU> dmocsny@minerva.che.uc.edu (Daniel Mocsny) writes: >If RISC gets 5 years ahead of CISC in hardware speed, that will be >enough to counter its software lag, which is probably of the same >order. (I.e., if present trends continue, the software available in >5 years for the current major RISC families, assuming they preserve >binary compatibility, *might* resemble the software available NOW for >the 80x86 family, in terms of range and price. However, leading-edge >hardware seems hard-pressed to maintain binary compatibility very >far backwards. This is *precisely* the software advantage and >hardware disadvantage of CISC.) >Do comp.arch pundits see RISC chips widening their gap over the >CISC chips? If the performance gap stays at a factor of two or three, >that represents a ~2 year hardware delay for CISC, which doesn't seem >large compared to the ~5 year software lead for CISC. Also, consider >that very few individual users are able to keep even a '386 machine >busy all the time. To do even that is an intense, full-time job for >anyone whose problem can't be solved in one "for" loop. >average Sparcstation, primarily because the average PC or Mac user can >afford more applications. The average useful program, if available >under UNIX, costs 2--10 times as much as the DOS or Mac equivalent. >This problem isn't going away anytime soon. > >Of course, since CISC and RISC are Turing-equivalent, there is no >fundamental reason why the software lead of CISC should be immutable. >In the real world, however, transparent portability across >architectures appears elusive, for a variety of reasons, and most >of them seem rather silly. All of this sounds like a plausible argument ... 6 years ago. So, explain why almost every major computer company (and now including most of the larger PC companies) either is already shipping a RISC-based product..... Are they all fools? Note that "the i386 is enough" is looking through the rear-view mirror; you can do some terrific things if you can get 50-100 mips cheap; (mostly to make computers a lot easier to use). Aggressive software developers out there understand this and are working in that direction, because it's going to happen. ------------ Following note is to somebody from CMU that asked about cfc1 instruction, but whose mail I lost somewhere: cfc1 stalls until all operations complete; the double cfc1s you saw should not be there, there was some case for an old FP board years ago, but the double cfc1 should be long gone. -- -john mashey DISCLAIMER: <generic disclaimer, I speak for me only, etc> UUCP: mash@mips.com OR {ames,decwrl,prls,pyramid}!mips!mash DDD: 408-524-7015, 524-8253 or (main number) 408-720-1700 USPS: MIPS Computer Systems MS 1/05, 930 E. Arques, Sunnyvale, CA 94088-3650