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From: josh@polaris.UUCP (Josh Knight)
Newsgroups: net.arch,net.unix
Subject: Re: ELXSI System 6400 .... Information needed
Message-ID: <596@polaris.UUCP>
Date: Sat, 21-Jun-86 19:46:55 EDT
Article-I.D.: polaris.596
Posted: Sat Jun 21 19:46:55 1986
Date-Received: Mon, 23-Jun-86 03:52:48 EDT
References: <203@cybavax.UUCP> <1946@calmasd.CALMA.UUCP> <120@portal.UUcp>
Reply-To: josh@polaris.UUCP (Josh Knight)
Distribution: net
Organization: IBM Research, Yorktown Heights, N.Y.
Lines: 25
Keywords: system performance multiprocessor
Xref: linus net.arch:3254 net.unix:7651
Summary: More processors MAY mean more memory, less context switching

In article <120@portal.UUcp> jel@portal.UUcp (John Little) writes:
>In article <1946@calmasd.CALMA.UUCP>, rfc@calmasd.CALMA.UUCP (Robert Clayton) writes:
>> a 10 processor test at Sandia Labs they got 10.1X the power of a single
>> processor.  
>
>This is an interesting trick. Does anyone have a clue about how they
>got a greater than linear speedup?  Was this a cpu benchmark or did
>it include i/o?  Can I program my single processor to emulate a
>multiprocessor configuration and get increased performance :-) ?
>

We certainly don't have any of these things here, but I should think
that more processors might mean more memory.  On a time sharing workload,
more memory could mean better performance, enough to hide whatever extra
(if any) software cost was involved.  If you have 10 people editing
and 10 CPU's you may do many fewer context switches with concomittant
reduction software costs not to mention (perhaps) fewer cache misses.
There are lots of ways it COULD happen; however, like John, I'm a Little
(sorry John) skeptical.

Of course I don't speak for IBM, only me.
-- 

	Josh Knight, IBM T.J. Watson Research
 josh@ibm.com, josh@yktvmh.bitnet,  ...!philabs!polaris!josh