Path: utzoo!mnetor!uunet!husc6!bloom-beacon!gatech!udel!princeton!phoenix!pupthy2!lgy From: lgy@pupthy2.PRINCETON.EDU (Larry Yaffe) Newsgroups: comp.arch Subject: Re: RISC a short answer?? Message-ID: <2810@phoenix.Princeton.EDU> Date: 7 May 88 18:38:00 GMT References: <1036@nusdhub.UUCP> <1988May3.224604.2252@utzoo.uucp> <383@m3.mfci.UUCP> <1988May5.171444.849@utzoo.uucp> <9341@apple.Apple.Com> Sender: news@phoenix.Princeton.EDU Reply-To: lgy@pupthy2.PRINCETON.EDU (Larry Yaffe) Organization: Physics Dept, Princeton Univ Lines: 43 In article <9341@apple.Apple.Com> bcase@apple.UUCP (Brian Case) writes: >In article <1988May5.171444.849@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >>Reduced Instruction Set means fewer and less complex instructions. That >>is all it means. > >Wow, I didn't think I'd ever see this comment. [...] >let me now give my personal, back-of- the-business-card summary of RISC: >1) Uniform Pipeline (all, or nearly all, instructions flow through the >pipeline in the same way) >2) Good match to optimizing compiler technology (the architecture makes it >easy for the compiler in several ways: code generation, code motion, >register allocation, etc., and *calculating the cost of code sequences* in >both time and space) >3) Allows technology to be exploited (cycle time dominated by some >"irreducible" component of computation like an ALU or Cache lookup; yes, I >know you can pipeline ALUs and cache lookups, but do you really want to?) These all seem like reasons for "Why RISC is a good thing", not at all part of the basic definition of what RISC stands for. Seems to me that Henry summed up what RISC means pretty well - fewer instructions. >RISC is a way of doing things, not a thing. This sounds like usurping the name of something specific (Reduced Instruction Set) for a much more general philosophy (into which it naturally fits). I'd call that a misleading choice of terminology. But then I don't have any simple acronym which sums up a philosophy of "keep things simple, devote resources & effort where they produce the most benefit". (Except for "common sense" :-)) . . . . . ------------------------------------------------------------------------ Laurence G. Yaffe lgy@pupthy.princeton.edu Department of Physics lgy@pucc.bitnet Princeton University ...!princeton!pupthy!lgy PO Box 708, Princeton NJ 08544 609-452-4371 or -4400