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From: bartho@obs.unige.ch (PAUL BARTHOLDI, OBSERVATOIRE DE GENEVE)
Newsgroups: comp.sys.m68k,comp.arch
Subject: Re: Moto's data predicts 68040 performance well below 20 MIPS
Message-ID: <713@obs.unige.ch>
Date: 17 Jul 90 08:50:41 GMT
References: <1990Jul13.163849.4282@msuinfo.cl.msu.edu> <6535.26a0e67f@vax1.tcd.ie>
Organization: University of Geneva, Switzerland
Lines: 30

In article <6535.26a0e67f@vax1.tcd.ie>, rwallace@vax1.tcd.ie writes:
> In article <1990Jul13.163849.4282@msuinfo.cl.msu.edu>, fox@VIXEN.NSCL.MSU.EDU writes:
>> 
>> For much of the stuff we run, 16Mhz 68020 + 68881 runs at about .8 VAX
>> mips. (Scientific technical applications). So it seems to me that
>> 25Mhz could be no faster than 25/16 * .8 = 1.25 VAX mips.
> 
> Sounds like either we don't agree on what VAX MIPS mean or there's something
> seriously wrong with your system or benchmarks. The 68000 at 8MHz is rated at
> about .8 MIPS. The 68020 at 16MHz should run about 3-4 MIPS (factor of 2 for
> the clock rate, factor of 2-3 for the better design). OK, processors run below
> rated performance with depressing frequency for reasons like not enough cache
> memory, badly written code etc. but by a factor of 4??? Are you sure you
> weren't running a benchmark that proves your compiler produces code that only
> runs 25% as fast as it should?
> 
> Russell Wallace, Trinity College, Dublin
> rwallace@vax1.tcd.ie
> "To summarize the summary of the summary: people are a problem"

We have a vax 780 with FPA (== 1 MIPS) and sun 3/60 at 16 MHz with 68881, that
is the same configuration as above.  All my comparisions show the sun to be
between .5 and .8 of the vax for pure computational tasks (no io).  One 
exception, TeX runs about twice as fast on the sun ... why ?  In all cases,
I used optimization, with the fortran compiler and standard libraries (TeX
is written in pascal or C), on real problems we have run on many other machines
too.  So Russells data are correct for me.  Who has a 68020/68881 that runs
3-4 times faster than a 780 ?

                                      Paul Bartholdi, Geneva Observatory