Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!bu-cs!bloom-beacon!apple!oliveb!sun!chiba!khb
From: khb%chiba@Sun.COM (chiba)
Newsgroups: comp.sys.sgi
Subject: Re:  Benchmark comparison of DEC 3100 and 4D/70GT
Message-ID: <97051@sun.Eng.Sun.COM>
Date: 31 Mar 89 22:16:29 GMT
References: <8903311650.AA03992@aero4.larc.nasa.gov>
Sender: news@sun.Eng.Sun.COM
Reply-To: khb@sun.UUCP (chiba)
Organization: Sun Microsystems, Mountain View
Lines: 39

In article <8903311650.AA03992@aero4.larc.nasa.gov> blbates@AERO4.LARC.NASA.GOV (Bates TAD/HRNAB ms294 x2601) writes:
>
>    I am not familiar with the Dhrystone test, but if it has a
>lot of integer math, that will slow it down on the Cray.  On the
>Cray's real math is faster than integer math.  Don't ask me why,
>it is a known fact.  The Cray's are optimized for real math and
>they don't care about integers.
>--

Dhrystone is _purely_ an integer test. It is basically worthless for
predicting performance of real code, but since a wide variety of
periodicals (Byte, et al) and netfolk insist on running it, and
publishing the results manufacter's of small computers do pay
attention (some more so than others, note the flap in comp.arch re:
intel 860 performance :>).

Cray customers benchmark the machines the old fashion way....they take
their real codes to cray (or reasonable subsets thereof) and have them
run them. (so, btw does Sun). This is the only way to really judge a
computer, have those who know how to tickle the beastie run your real
codes and faithfully report what happened, and how.

Those who have small budgets rely on the press/net to give them the
best info they can .... and thus Dhrystones lives on...and on....

Cray's actually have a good balance between integer and FP....for the
class of applications for which the machine was designed (i.e.
numerical math...so integers are for do-loop indicies and address
computation only). If your application is different (say symbolic
computation or certain types of circuit simulation) you may find that
a very different machine is what the doctor ordered.

Well enough pontificating for now. I return you to your regularly
scheduled sgitalk :>



Keith H. Bierman
It's Not My Fault ---- I Voted for Bill & Opus