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Memory size equivalences
Date: Tue, 11 Dec 90 13:30:07 -0800
From: firstname.lastname@example.org (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.
>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).