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From: lamaster@pioneer.arpa (Hugh LaMaster)
Newsgroups: comp.arch
Subject: Re: brash micros ... [really: CPI versus (cycles)/(work)]
Message-ID: <2716@ames.arpa>
Date: Wed, 9-Sep-87 12:56:15 EDT
Article-I.D.: ames.2716
Posted: Wed Sep  9 12:56:15 1987
Date-Received: Fri, 11-Sep-87 02:12:51 EDT
References: <622@winchester.UUCP> <12953@amdahl.amdahl.com>
Sender: usenet@ames.arpa
Reply-To: lamaster@ames.UUCP (Hugh LaMaster)
Organization: NASA Ames Research Center, Moffett Field, Calif.
Lines: 37

In article <667@winchester.UUCP> mash@winchester.UUCP (John Mashey) writes:

>ones.  CPI's DON'T EXIST APART FROM BENCHMARKS.  For example, on the same
>CPU:
>	1.05	small loopy benchmark that fits in caches [Dhrystone]
>	2-3	bigger one, with some FP, or cache misses, depending on
>		memory system [Hspice]
>	30+	handcoded program that does mostly integer divides

Exactly right.  I only consider cycles per instruction to be useful when
measured using the LINPACK benchmark myself :-)   [Weitek, Fairchild, MIPS,
and to a lesser extent Sun, Motorola, and AMD all seem to be taking floating
point very seriously now.  Thanks, folks.]  Many people out there would no
doubt prefer using a Un*x oriented benchmark with lots of typical utilities,
fork and exec exercizers, TCP/IP/network &etc. stuff, rn ...  It all depends
upon the set of applications that you will run on the machine.  The benchmarks
used to measure the performance of the machine for your applications also can
measure the "architectural efficiency" in various ways for your applications.
IF you care.  Presumably, an end user wouldn't care about it anyway, except
out of curiosity, since the net performance is what the user sees, not the
design tradeoffs of system architects.






  Hugh LaMaster, m/s 233-9,  UUCP {seismo,topaz,lll-crg,ucbvax}!
  NASA Ames Research Center                ames!pioneer!lamaster
  Moffett Field, CA 94035    ARPA lamaster@ames-pioneer.arpa
  Phone:  (415)694-6117      ARPA lamaster@pioneer.arc.nasa.gov


                 "IBM will have it soon"


(Disclaimer: "All opinions solely the author's responsibility")