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From: chuck@amdahl.UUCP
Newsgroups: comp.arch
Subject: Re: shared memory multiproc. question
Message-ID: <5713@amdahl.UUCP>
Date: Fri, 20-Feb-87 22:26:28 EST
Article-I.D.: amdahl.5713
Posted: Fri Feb 20 22:26:28 1987
Date-Received: Sat, 21-Feb-87 17:36:21 EST
References: <76700001@uiucdcsp> <rocheste.24385> <1205@ogcvax.UUCP> <5699@amdahl.UUCP> <1513@im4u.UUCP>
Reply-To: chuck@amdahl.UUCP (Charles Simmons)
Distribution: na
Organization: Amdahl Corp, Sunnyvale CA
Lines: 27

In article <1513@im4u.UUCP> suhler@im4u.UUCP (Paul A. Suhler) writes:
>In article <5699@amdahl.UUCP> chuck@amdahl.UUCP (Charles Simmons) writes:
>>Seeing how two different people suggested that distributed memory is
>>inappropriate for multiple users running independent tasks, maybe someone
>>could tell me why.  I find it hard to imagine a problem which is more
>>partitionable.  Since the tasks are independent, each user should be very
>>happy to have her very own address space.  
>
>This is true only if the machine has a decent I/O architecture, i.e.,
>enough paths among local memories and disk(s).  Imagine trying to squeeze
>page swaps over multiple inter-node links.  The situation with Intel's
>iPSC isn't much better:  a single ethernet linking a single disk with
>32 to 128 nodes.  Rumor has it that they're well aware of the problem
>and will fix it in the next incarnation.
>Paul Suhler        suhler@im4u.UTEXAS.EDU	512-474-9517

Let's assume that each workstation has a 20Mb hard disk for cacheing
I/O to the network.  It may take a few minutes to load a working set
of programs and data into the cache over a 40K baud ethernet link,
but after that, things should hum pretty well.  20Mb is enough to
do a substantial amount of page swapping (even if the 8Mb of local
ram won't hold your programs) as well as hold most of the useful files
associated with Unix.  If you don't turn your machine off at night,
you won't even be slowed down by having to reload your working set
every mornining.

-- Chuck