Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!ames!think!bloom-beacon!mit-eddie!uw-beaver!uw-june!pardo
From: pardo@june.cs.washington.edu (David Keppel)
Newsgroups: comp.arch
Subject: Cray & Amdahl (Was: missing Dhrystone 2.1)
Summary: Virtual memory?
Message-ID: <5342@june.cs.washington.edu>
Date: 21 Jul 88 17:50:04 GMT
References: <4232@cbmvax.UUCP> <76700035@p.cs.uiuc.edu> <9a0K/cbluk1010IHSPc@amdahl.uts.amdahl.com> <228@sdeggo.UUCP>
Reply-To: pardo@uw-june.UUCP (David Keppel)
Organization: U of Washington, Computer Science, Seattle
Lines: 20

[ Comparisons of Amdahls, Crays, 68Ks, and an 11/750 ]
[ Cray 1Gb, Amdahl 256Mbyte ]

I believe (please correct me if I'm wrong ...) that the Cray's memory
limit is ~750Mword (* 8 bytes/word = ~6Gb) but that few machines have
anywhere near this much.

More to the point, I also believe that the Crays don't have virtual
memory (because it slows down the computer!) while the Amdahls do
(have virtual memory).

Relevant (really?) question: Does it make more sense to buy a little
bit of very fast memory and slow it down with virtual memory, or to
buy a whole bunch of fast physical memory and slow it down by putting
it farther away?  (Assume: $ is no problem).  Obviously the answer
depends on the access patterns (and dataset size) of the programs
being run.  I wonder if anybody has insight on this?


	;-D on  ( Registers for me )  Pardo