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From: roy@phri.UUCP (Roy Smith)
Newsgroups: comp.arch,comp.sys.misc,comp.unix.wizards
Subject: Re: Between a Sun-4 and a Cray-2
Message-ID: <2866@phri.UUCP>
Date: Fri, 21-Aug-87 13:26:00 EDT
Article-I.D.: phri.2866
Posted: Fri Aug 21 13:26:00 1987
Date-Received: Sun, 23-Aug-87 05:02:11 EDT
References: <7500@shemp.UCLA.EDU> <552@winchester.UUCP>
Reply-To: roy@phri.UUCP (Roy Smith)
Distribution: world
Organization: Public Health Research Inst. (NY, NY)
Lines: 37
Xref: mnetor comp.arch:1860 comp.sys.misc:770 comp.unix.wizards:3820

In article <552@winchester.UUCP> mash@winchester.UUCP (John Mashey) writes:
> We got this [[7 or so mips rating for Sun-4 as opposed to the 10 mips Sun
> claims -- RHS]] from looking carefully at the published data, filling in
> some holes in the tables, and cross-comparing with other RISC systems.
> [We've got a 40-pager that analyzes the data in detail, if anybody is
> interested.]

	John send me that 40-pager ("A Sun-4 Benchmark Analysis", July 23,
1987) at my request, and I've got a few comments.  First off, is I have
learned to take with a grain of salt *anything* a computer manufacturer
says about any other manufacturer's products.  With this disclaimer out of
the way, the report seems to make a lot of sense, at least on the surface.
The problem is that Sun claims 10 mips performance for the Sun-4, while
MIPS insists it's more like 7 mips.  That's a 30% difference, which in my
book just isn't that much for this type of calculation.

	Also, I don't like the performance graphs in the MIPS report.  The
graphs have "Performance" on the Y-axis and "Benchmark Type" on the X-axis,
with lines connecting the data points.  This is wrong, since it indicates
that "Benchmark Type" is a continious function, and implies that you can
interpolate between the data points to find values for intermediate types
of benchmarks.  These graphs should have been bar graphs, or scatter plots,
or some other type of plot which is more suitable to discrete data.  BTW,
the graphs look like they were done using CricketGraph on a Mac.  Very
pleasing to the eye, even if they are misleading. :-)

	One point made in the report, which I feel is vitally important, is
that floating point speed doesn't scale well with integer speed.  For us,
floating point is where it's at.  I believe the Sun-3/100, 3/200, and 4/200
series machines all use the same FPA, based on the Wietek chip set.  What
that means is that the 3/100 series has the "best" floating/integer speed
ratio, and the 4/200 series the "worst".  You get the same kind of
non-linearity with the Vax-750/780/785/8600/8[78]00 progression, I think.
-- 
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New AM serinalo
A=