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From: pop@mtu.UUCP (Dave Poplawski)
Newsgroups: net.arch
Subject: Re: I don't believe your statements about multiprocessors
Message-ID: <185@mtu.UUCP>
Date: Mon, 13-May-85 20:27:10 EDT
Article-I.D.: mtu.185
Posted: Mon May 13 20:27:10 1985
Date-Received: Thu, 16-May-85 07:25:23 EDT
References: <7202@Glacier.ARPA> <184@mtu.UUCP> <78@utastro.UUCP>
Distribution: net
Organization: Michigan Tech, Houghton, MI
Lines: 32

> > As soon as you can build a uniprocessor
> > that is as fast as any multiprocessor, the multiprocessors will go away.
> > -- 
> > Dave Poplawski
> 
> This makes no sense to me.  If you can build a really fast uniprocessor,
> why can't you run a bunch in parallel and get more thoughput?  Are you
> suggesting there may be a computer so fast no problem can keep it busy?
> My friends, the astrophysicists, don't believe that for a minute.
> 
> -- 
> Ed Nather

The statement was made in a whimsical voice  (couldn't  you  hear  it).   I
don't think that anybody will ever do it, probably because it is impossible
for  the  reason  you  stated.   However,  don't  count   out   very   fast
uniprocessors  -  I  wouldn't  want  to  try  to  get a 100-fold speedup on
something like troff by putting it on 100 (or even 200, or 300, or ...) cpu
multiprocessor.   Some  problems  just  don't  seem to be very amendable to
parallel solution, at least not that parallel.

An interesting question is whether the throughput you mention  is  realized
on a single problem, or several independent ones.  On a single problem that
must  be  broken  into  cooperating  processes,  it  is  possible  that   a
multiprocessor would be slower than the uniprocessor because of contention,
communication costs, synchronization  overhead  and  delay,  etc.   It  all
depends on the problem, the algorithm, the program, the multiprocessor, ...
-- 
Dave Poplawski
Michigan Technological University
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