Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!ncar!ico!rcd
From: rcd@ico.isc.com (Dick Dunn)
Newsgroups: comp.arch
Subject: Re: RISC reaching its limits?!?
Message-ID: <1991Jan28.184325.15815@ico.isc.com>
Date: 28 Jan 91 18:43:25 GMT
References: <1991Jan27.214225.26765@csusac.csus.edu>
Distribution: usa
Organization: Interactive Systems Corporation, Boulder, CO
Lines: 30

croft@csusac.csus.edu (Steve Croft) writes:
> I have heard from a non-RISC company and a magazine article that RISC is
> reaching its performance limits.  Why would this be so?  or not so?
> Inquiring minds wanna know...

I have heard from a newspaper that a dog gave birth to a two-headed human
baby.  One of the heads looks just like Elvis.  Why would this be so?  or
not so?  Enquirer minds wanna know... :-)

The burden of enumerating the reasons RISC might be reaching its perfor-
mance limits rests with the people who claim that's so.  The burden of
proof does not rest on the null hypothesis.  In other words, if someone
tells you RISC is running out of gas, have *them* back up their state-
ments.  There's no shortage of RISC nay-sayers.  Some of them have valid
points, but many simply have axes to grind.  (You're obviously aware of
this, since you point out that one of your sources is a "non-RISC
company.")  Why not find out their explanations and toss them at comp.
arch to see what the folks here have to say about them.

I'm not sure what it means for RISC to reach its performance limits.  It
will obviously take additional approaches to wring out more speed--such as
superscalar or (more likely?) superpipelining--but these really are
additions rather than replacements.  Moreover, these techniques really
build on the RISC approach, in that RISC gives you an easier base to work
from.  (Colwell, while he was at Multiflow, was fond of pointing out that
their VLIWs took a RISC approach.)

-- 
Dick Dunn     rcd@ico.isc.com -or- ico!rcd       Boulder, CO   (303)449-2870
   ...Mr. Natural says, "Use the right tool for the job."