Memory size equivalences

[jcma@reagan.ai.mit.edu (John C. Mallery)]

    Date: Tue, 11 Dec 90 13:30:07 -0800
    From: jbarnett@nrtc.northrop.com (Jeff Barnett)

    We are thinking of replacing several 36xx machines with the new 1200's.
    The 3600 machines each have either 4 or 6 mega-word memories.  From your
    experiences with similar conversions, can anyone estimate the amount of
    memory necessary for the 1200's to get similar performance.  By similar
    performance, I mean how much memory do I need so that I page thrash about
    the same fraction of the time that I do now.  I understand that this
    question is not particularly well-formed but I would appreciate any
    heuristic advise that is available.

	    Jeff

>From my experience, an XL1200 with 4 megawords of memory runs the same natural
language application 6 times faster with 10% of the page faults (if you belief
the time macro) as a 3640 with the same amount of memory.  This application is
memory-intensive because it builds a knowledge base from incoming sentences
and sentence may refer to prior knowledge.  Some of this performance doubtless
comes from using areas localize memory.  I suspect somebody fixed up paging
performance for the I-machine.  Perhaps someone on this list can tell us about
it. (Note that paging performance is currently one of the major advantages of
the lisp machine over unix lisps).