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From: crowl@rochester.UUCP (Lawrence Crowl)
Newsgroups: net.arch
Subject: Re: 11/08/85 Dhrystone Benchmark Results
Message-ID: <13143@rochester.UUCP>
Date: Thu, 14-Nov-85 12:41:19 EST
Article-I.D.: rocheste.13143
Posted: Thu Nov 14 12:41:19 1985
Date-Received: Fri, 15-Nov-85 05:44:40 EST
References: <1129@hou2h.UUCP> <643@cornell.UUCP>
Reply-To: crowl@rochester.UUCP (Lawrence Crowl)
Distribution: net.arch
Organization: U. of Rochester, CS Dept.
Lines: 29

In article <643@cornell.UUCP> jqj@cornell.UUCP (J Q Johnson) writes:
>....  One major question
>that remains in my mind with respect to Dhrystone benchmarks is the effect
>of cache.  Has anyone looked at Dhrystone benchmarks with this in mind?
>....

The Dhrystone benchmark originated in:

        Reinhold P. Weicker
        Dhrystone: A Synthetic Systems Programming Benchmark
        Communications of the ACM
        Volume 27, Number 10, Pages 1013-1030, October 1984

In the article, the benchmark is timed for only one run.  This eliminates the
effect of cache on multiple runs, but not for the single run, which is as it
should be.  Multiple runs will skew the results heavily towards machines with
a cache.  Multiple runs are a timing convenience and are not in the spirit of
a 'systems' benchmark because systems programs usually do not exibit this
behavior.  This convenience is acceptable for machines without ANY cache, but
it is not acceptable for machines with a cache.  Therefore, do not accept the
results of a multiple run timing on machines with a cache.  Insist that the
benchmarker get out a logic analyzer and time a single run.  I know this is a
major hassle, but it is the only comparable result.  I suggest you read the
article if you intend to use the results.
-- 

Lawrence Crowl             716-275-5766        University of Rochester
                                               Computer Science Department
...!{allegra,decvax,seismo}!rochester!crowl    Rochester, New York,  14627