Path: utzoo!utgpu!watserv1!watmath!iuvax!mailrus!ncar!ico!rcd
From: rcd@ico.isc.com (Dick Dunn)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Why The Move To RISC Architectures? (and meaningless MIPS)
Summary: rebutting a rebuttal
Message-ID: <1990Mar21.230854.318@ico.isc.com>
Date: 21 Mar 90 23:08:54 GMT
References: <28011@cup.portal.com> <40970054@hpindda.HP.COM> <2607b76e.5ca0@polyslo.CalPoly.EDU>
Organization: Interactive Systems Corporation, Boulder, CO
Lines: 27

jdudeck@polyslo.CalPoly.EDU (John R. Dudeck) writes:
> A few weeks ago I made the remark on the net that it seems meaningless to
> compare RISC MIPS with CISC MIPS.  I was soundly rebutted by any number
> of netters telling me that all the manufacturers use VAX MIPS
> when rating their cpu's.  In other words, benchmarks are run for various
> types of cpu-intensive applications, and the results are compared to the
> same benchmarks on a VAX 11/780, which is the platinum standard by which
> all cpu's are measured.

Would that it were so simple!  Manufacturers will run various benchmarks
and may quote one real number, one invented ("theoretical") number, the
best number they can get, lots of numbers, etc., with or without any
explanation or rationale.

Example - You may have seen the new IBM RISC boxes advertised as "27.5
MIPS".  That's based on ONE benchmark that's out of date and known to be
inadequate for any machine with a decent compiler.  The number is, in fact,
a comparison with a VAX number for the same benchmark.  However, if you
look at other numbers IBM has published for the RS/6000, you'll find that
it could be characterized as 15.8 MIPS (integer SPEC) or 22.3 MIPS (integer
plus FP SPEC).  The 15.8, 22.3, and 27.5 numbers are all relative to a VAX
11/780.  The differences are in what is measured and whether the
measurement is realistic.  But if you're comfortable with the idea that
15.8 is almost the same as 27.5, then MIPS figures make sense...
-- 
Dick Dunn     rcd@ico.isc.com    uucp: {ncar,nbires}!ico!rcd     (303)449-2870
   ...Relax...don't worry...have a homebrew.