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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.arch
Subject: Re: Re: I don't believe your statements abou
Message-ID: <5593@utzoo.UUCP>
Date: Tue, 14-May-85 12:09:34 EDT
Article-I.D.: utzoo.5593
Posted: Tue May 14 12:09:34 1985
Date-Received: Tue, 14-May-85 12:09:34 EDT
References: <7202@Glacier.UUCP> <36900002@ima.UUCP>, <579@lll-crg.ARPA>
Organization: U of Toronto Zoology
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Actually, in Computing Surveys some years ago there was mention of another
case where a multiprocessor got super-linear performance.  "Multi" in that
case was 2, so it's not a striking example, but even so it was interesting.
The machine was a dual-processor IBM 360/67.  The slightly-better-than-2
factor of performance was because some system overhead is not proportional
to the user load, and that overhead has to be incurred only once for both
processors.  The 67 had an unusual i/o architecture that tended to direct
interrupts to the processor (if any) that wasn't busy at the time, which
helped.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry