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From: jjw@celerity.UUCP (Jim )
Newsgroups: net.arch
Subject: Re: VERY LARGE main memories
Message-ID: <589@celerity.UUCP>
Date: Tue, 30-Sep-86 12:15:56 EDT
Article-I.D.: celerity.589
Posted: Tue Sep 30 12:15:56 1986
Date-Received: Mon, 6-Oct-86 18:43:02 EDT
References: <1130@bu-cs.bu-cs.BU.EDU> <7144@lanl.ARPA> <7148@lanl.ARPA> <609@nike.UUCP> <7839@lanl.ARPA> <627@nike.UUCP> <7965@lanl.ARPA>
Reply-To: jjw@celerity.UUCP (Jim (JJ) Whelan)
Organization: Celerity Computing, San Diego, Ca.
Lines: 31
Keywords: virtual memory

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 with the following characteristics:

	They are pushing the "state of the art" in memory and processor
	design.

	They are intended for large scale, vectored, mostly floating point
	calculations.

	They are expensive to purchase and operate.

	They are usually sold and purchased to support a few computationally
	intensive applications (which may run for hours or days even on a
	Cray).

In this environment virtual memory is probably a hindrance rather than a help.

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.


---------
* 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?