Path: utzoo!mnetor!uunet!mfci!root
From: root@mfci.UUCP (SuperUser)
Newsgroups: comp.arch
Subject: Re: RISC  a short answer??
Message-ID: <388@m3.mfci.UUCP>
Date: 8 May 88 15:00:53 GMT
References: <1036@nusdhub.UUCP> <1988May3.224604.2252@utzoo.uucp> <383@m3.mfci.UUCP> <1988May5.171444.849@utzoo.uucp> <9341@apple.Apple.Com> <2810@phoenix.Princeton.EDU>
Reply-To: colwell@m3.UUCP (Robert Colwell)
Organization: Multiflow Computer Inc., Branford Ct. 06405
Lines: 66

In article <2810@phoenix.Princeton.EDU= lgy@pupthy2.PRINCETON.EDU (Larry Yaffe) writes:
=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.
=

Nope, Henry missed the boat.  You both are basically citing the
definition that Patterson originally proffered, taking us to task for
trying to change that.  But if you want to be historically accurate,
then start with Radin's ASPLOS-I paper on the IBM-801, which does not
talk about the number of instructions but about their efficacy and
usefulness.

And if you still insist that RISC stand for 1981-1983's "few instrs"
phase, then we may as well dump the acronym and get another, because
yours is of no interest any more.

==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" :-))
                             ^^^^^^^^^^^^^^
See, we agree on something!  As per my comment above, I think you
have been fooled by the definition that was in vogue for a short
while.  If you want historical accuracy, read Radin and forget your
"few instrs" idea.  If you want useful ideas, consider broadening
your perspectives on RISC.  Thinking that RISC only constitutes
a recipe for designing an instruction set is (and was) a useless
viewpoint. 

So maybe we're all agreeing that "R.I.S.C." is a bad acronym (it also
stands for Rhode Island Seafood Council, by the way), and we need
some other one to avoid misunderstandings.  But I just haven't quite
been able to accept HP's "Streamlined" or "Precision" nomenclature...

=------------------------------------------------------------------------
=Laurence G. Yaffe			lgy@pupthy.princeton.edu

Bob Colwell            mfci!colwell@uunet.uucp
Multiflow Computer
175 N. Main St.
Branford, CT 06405     203-488-6090