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Article #2873Re: VERY LARGE main memories
From: Peter Montgomery
Date: Thu, 18 Sep 1986 01:29
Date: Thu, 18 Sep 1986 01:29
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I once was a system programmer for a CDC 7600 site. We ran many
scientific programs, but lacked virtual memory. Some programs used almost
all of memory. These jobs might run faster than the same ones would with
less memory, but overall system performance suffered. For example, a
compilation might not fit in memory alongside a huge scientific job. If
the compilation runs alone, the CPU will be idle much of the time it runs.
Yet the scientific program might have considerable unused code and/or data
(e.g., the input data for this run does not select Calcomp plots, so those
routines are never called and their data areas are never referenced;
another likely possibility is that some dimensions are much larger than
required). If either job runs alone, then it wants as much memory as it
can get. With virtual memory, the operating system can simultaneously
load the heavily used parts of BOTH jobs in the machine, for better
overall performance.
--
Peter Montgomery
{aero,allegra,bmcg,burdvax,hplabs,
ihnp4,psivax,randvax,sdcsvax,trwrb}!sdcrdcf!pmontgom
Don't blame me for the crowded freeways - I don't drive.
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Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: arc1-ca.pugleaf.net!utzoo!mnetor!seismo!ll-xn!nike!oliveb!hplabs!sdcrdcf!pmontgom From: pmontgom@sdcrdcf.UUCP (Peter Montgomery) Newsgroups: net.arch Subject: Re: VERY LARGE main memories Message-ID: <3013@sdcrdcf.UUCP> Date: Wed, 17-Sep-86 21:29:54 EDT Article-I.D.: sdcrdcf.3013 Posted: Wed Sep 17 21:29:54 1986 Date-Received: Fri, 19-Sep-86 23:17:28 EDT References: <1130@bu-cs.bu-cs.BU.EDU> <7144@lanl.ARPA> Reply-To: pmontgom@sdcrdcf.UUCP (Peter Montgomery) Organization: System Development Corporation R&D, Santa Monica Lines: 22 Keywords: VM economy tradeoff