Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!ucsd!ucbvax!agate!shelby!portia.stanford.edu!dhinds
From: dhinds@portia.Stanford.EDU (David Hinds)
Newsgroups: comp.arch
Subject: Re: Benchmarks from Hell
Keywords: RS/6000, i468, Enquirer
Message-ID: <1990Aug30.182437.9759@portia.Stanford.EDU>
Date: 30 Aug 90 18:24:37 GMT
References: <631@stdc01.UUCP> <2475@crdos1.crd.ge.COM>
Organization: AIR, Stanford University
Lines: 32

In article <2475@crdos1.crd.ge.COM> davidsen@crdos1.crd.ge.com (bill davidsen) writes:
>In article <631@stdc01.UUCP> mjones@stdc01.UUCP (Michael Jones) writes:
>
>[ Neal Norman said the 486 was faster than the RS6000 for fp in awk! ]
>
>  I haven't looked up the article you mention, but we had a good talk
>about selection of benchmarks to prevent vectorization *for testing
>scalar performance* some years ago at UNIforum, so I can believe that
>for testing some particular thing he may well have used awk. I doubt
>that he was looking for max fp performance on that test, though. Let's
>wait for the whole story.
>
    The mini-pre-review says that an HP Vectra 486 is 20% faster than
an IBM RS6000-320 on integer and FP calculations.  To explain the results,
the article quotes the benchmarkers as saying that this could either mean
IBM has a slow awk, or it has slow FP.  This definitely implies that their
ultimate measure of FP performance was awk.

    I tried running some tests on a 320 yesterday, to compare it with our
SGI 4D/240 system.  On some Fortran float-intensive code, the 320 was
marginally faster than the 25 MHz R3000/3010 in single precision, and
nuch (2X) faster in double precision.  On some C mixed but mostly integer
code, the R3000 came out a bit faster.  This system still had old pre-
release software, so the compilers may have improved.  C seems like a
tricky choice of language for FP comparison, given the differences in
implementations as to promotion of single to double precision.  K&R says
that floats should be promoted to double in all expressions, but ANSI says
they don't have to.  This makes a big difference on my SGI code, but
I don't know what the IBM compiler was doing.

 -David Hinds
  dhinds@popserver.stanford.edu