Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!amdahl!nsc!voder!apple!baum
From: baum@Apple.COM (Allen J. Baum)
Newsgroups: comp.arch
Subject: CRAY vs. caching & VM
Message-ID: <14493@apple.Apple.COM>
Date: 22 Jul 88 16:25:28 GMT
References: <4232@cbmvax.UUCP> <76700035@p.cs.uiuc.edu> <5342@june.cs.washington.edu> <60952@sun.uucp>
Reply-To: baum@apple.UUCP (Allen Baum)
Organization: Apple Computer, Inc.
Lines: 11

[]

Although one possible reason for avoiding caching and virtual memory might be
performance, and the philosophical implications thereof (lose .x% performance,
but save .y% by not having to worry about z), there is a very good reason for
not having it in a CRAY. The CRAY is statically scheduled; compilers and
humans spend a LOT of time optimizing the order of instructions to tweak every
last cycle out of program. They can do this because they can predict, every
time, exactly when an operation will be finished. This is not true in the
presence of cache misses or page faults.

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