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From: kent@decwrl.UUCP
Newsgroups: comp.arch
Subject: Re: Will caches ever become obsolete?
Message-ID: <8419@decwrl.DEC.COM>
Date: Tue, 3-Mar-87 15:44:24 EST
Article-I.D.: decwrl.8419
Posted: Tue Mar  3 15:44:24 1987
Date-Received: Fri, 6-Mar-87 02:36:21 EST
References: <3182@wateng.UUCP> <4765@shemp.ucla-cs.UCLA.EDU>
Reply-To: kent@decwrl.UUCP (Christopher A. Kent)
Distribution: comp
Organization: DEC Western Research Laboratory
Lines: 24
Keywords: cache, coherence problems

Even if the performance of the memory hierarchy in the CPU (or main processor
assembly in the case of a multiprocessor) becomes a moot point because
the relative performance is small, current research in cache consistency
algorithms will still be useful. 

There's a whole range of memory hierarchy that isn't being considered -- what
about that disk you have hanging out there? Technology has made this
portion of the memory hierarchy less and less visible (no longer do we have
a small paging drum that acts as a cache for a slower, larger paging
disk, for example), but it's still there, and still critical to good
performance. In fact, with the introduction of remote file systems in
computing systems distributed across a LAN, the relative performance
of main memory to backing/paging stores is worse than it used to be.

Much research is still needed to apply cache technology to this portion
of the memory hierarchy, and main memory cache consistency seems to be
a good place to start. My thesis research looked at adapting various
multiprocessor cache consistency schemes to a distributed file system;
some worked out quite nicely.

chris
-- 
Chris Kent	Western Research Laboratory	Digital Equipment Corporation
kent@decwrl.dec.com	decwrl!kent			(415) 853-6639