Path: utzoo!mnetor!uunet!lll-winken!lll-crg.llnl.gov!brooks
From: brooks@lll-crg.llnl.gov (Eugene D. Brooks III)
Newsgroups: comp.arch
Subject: Re: Was: RISC is a nasty no-no! Mor
Message-ID: <4712@lll-winken.llnl.gov>
Date: 9 Mar 88 21:17:47 GMT
References: <7690@pur-ee.UUCP> <3300021@uiucdcsm>
Sender: usenet@lll-winken.llnl.gov
Reply-To: brooks@lll-crg.llnl.gov.UUCP (Eugene D. Brooks III)
Organization: Lawrence Livermore National Laboratory
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In article <3300021@uiucdcsm> grunwald@uiucdcsm.cs.uiuc.edu writes:
>
>re: address hashing to randomize bank conflicts.
>
>I would think that this would be too slow in software. However, if I recall
>correctly, randomized hashing was done in hardware on the RP-3 (it had some
>sort of variable hashing so you could fiddle with the parameters).

Those who have been using supercomputers for the past decade have dealt
with this sort of problem by carefully avoiding the undesired addressing
modes.  Hashing takes care of the few pathological cases by slowing down
the majority of cases which would normally stream at one word per clock.
To slow down the machine to "random gather" speed for all of the normally
high performance situtations is not desired.  This applies to shared memory
multiprocessors as well as it does to single cpu supercomputers.