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From: reiter@endor.UUCP
Newsgroups: comp.arch
Subject: Re: Will caches ever become obsolete?
Message-ID: <1341@husc6.UUCP>
Date: Wed, 4-Mar-87 11:31:49 EST
Article-I.D.: husc6.1341
Posted: Wed Mar  4 11:31:49 1987
Date-Received: Fri, 6-Mar-87 06:04:55 EST
References: <3182@wateng.UUCP>
Sender: news@husc6.UUCP
Reply-To: reiter@harvard.UUCP (Ehud Reiter)
Distribution: comp
Organization: Aiken Computation Lab Harvard, Cambridge, MA
Lines: 22
Keywords: cache, coherence problems

In article <3182@wateng.UUCP> hmthaker@wateng.UUCP (Hemi M. Thaker) writes:
>that the speed of say, a 1Mb chip will be comparable to that
>of say a 1Kb ECL chip used in current caches?
>     In other words, will all the research being conducted
>for the cache coherency problems be a waste?

Even if processor and memory chips are made with the same technology,
the processor can access on-chip memory much faster than off-chip memory.
So, even if CMOS is as fast as ECL, we still may want to make a cache of
our processor's on-chip memory.

Also, main memory is typically shared accessed by a bus with several masters
(DMA I/O devices as well as CPU, perhaps several CPU's in a shared-memory
multiprocessor), so somewhat complex (and slow) bus protocols may be
required, and memory bandwidth must be shared.  Processors may still
benefit from a private unshared cache memory, even if the cache's memory
chips are no faster than main memory's memory chips.

I think caches will be around for quite a while!

					Ehud Reiter
					reiter@harvard (ARPA,BITNET,UUCP)