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From: jlg@lanl.ARPA (Jim Giles)
Newsgroups: net.arch
Subject: Re: VERY LARGE main memories
Message-ID: <8518@lanl.ARPA>
Date: Sun, 12-Oct-86 09:26:54 EDT
Article-I.D.: lanl.8518
Posted: Sun Oct 12 09:26:54 1986
Date-Received: Fri, 17-Oct-86 09:07:14 EDT
References: <1130@bu-cs.bu-cs.BU.EDU> <7144@lanl.ARPA>
Reply-To: jlg@a.UUCP (Jim Giles)
Organization: Los Alamos National Laboratory
Lines: 29
Keywords: virtual memory

In article <589@celerity.UUCP> jjw@celerity.UUCP (Jim (JJ) Whelan) writes:
>The "anti-virtual" memory discussions seem to be concentrating on whether
>Supercomputers need virtual memory.  Note that these machines are in a sense
>special purpose* machines ...
>...
>However, as time passes, larger memories and faster processors will be
>available for more conventional general purpose computers.  I believe that
>virtual memory will be essential for the management of the larger memories
>in many of the environments in which these systems will be used.
>
This has been my point all along.  I never claimed that virtual memory
was universally bad, only that it is counterproductive in SOME
applications.  The main opposition to this view has come from those
supporters of VM who think that all applications are better with VM.

>---------
>* I know they are special purpose in the sense that they can perform any
>  application which any other "general purpose" machine can perform.  But,
>  how many people purchase a Cray to do timesharing, text editing or
>  business EDP?  And if they do what do you suppose Seymore Cray's answer
>  would be to someone who complains about the number of users who can get
>  good emacs response?

It is interesting to note however, that Crays have a better price-
performance ratio, even on these tasks, than VAXEN do.  But then,
nearly everything has a better price-performance ratio than a VAX!

J. Giles
Los Alamos