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From: turner@uicsrd.csrd.uiuc.edu.UUCP
Newsgroups: comp.arch
Subject: Re: Is Shared Memory Necessary?
Message-ID: <43700039@uicsrd.csrd.uiuc.edu>
Date: 18 May 88 18:18:00 GMT
References: <685@thalia.rice.edu>
Lines: 34
Nf-ID: #R:thalia.rice.edu:685:uicsrd.csrd.uiuc.edu:43700039:000:1793
Nf-From: uicsrd.csrd.uiuc.edu!turner    May 18 13:18:00 1988
Posted: Wed May 18 14:18:00 1988


/* Written 11:31 am  May 10, 1988 by retrac@titan.rice.edu in comp.arch */

...                     The RP-3 project at IBM is doing some interest-
ing work on large shared memory architectures.  Their work aside, I think that
you should be able to get "optimal" performance by providing very fast
dsistributed memory communication, hardward support for IPC (interprocess[or]
communication), intelligent/clever communication protocols, and intelligent
compilers that can schedule the IPC so as to remove or reduce the delay
associated with waiting for remote memory access. ...

John Carter               Internet: retrac@rice.edu
Dept of Computer Science  CSNET:    retrac@rice.edu
Rice University           UUCP:     {internet node or backbone}!rice!retrac
Houston, TX
/* End of text from uicsrd.csrd.uiuc.edu:comp.arch */

For "optimal" performance on *some* applications, local memories and
fast interprocessor communication may well be enough.  But for others
communication costs may well eliminate any speedup due to parallelism.

Why is it that everyone seems to assume that machines must either have
shared memory OR distributed memory, never a little of both?  From my
point of view I would like to see a machine with: fast local memory;
slower, but deeply pipelined, shared memory; and a thin global sync
bus (for barrier sync).  We have had memory heirarchies for decades
now, why should they cease to be useful now?
---------------------------------------------------------------------------
 Steve Turner (on the Si prairie  - UIUC CSRD)

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