Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!labrea!rutgers!cmcl2!yale!mfci!rodman
From: rodman@mfci.UUCP (Paul Rodman)
Newsgroups: comp.arch
Subject: Re: Don't look back
Message-ID: <676@m3.mfci.UUCP>
Date: 27 Feb 89 15:35:27 GMT
References: <20667@lll-winken.LLNL.GOV> <7330@pyr.gatech.EDU> <656@m3.mfci.UUCP> <7367@pyr.gatech.EDU>
Sender: rodman@mfci.UUCP
Reply-To: rodman@mfci.UUCP (Paul Rodman)
Organization: Multiflow Computer Inc., Branford Ct. 06405
Lines: 44

In article <7367@pyr.gatech.EDU> mccalpin@loligo.cc.fsu.edu (John McCalpin) writes:
>
>If you re-read my original message, you will see that I am talking about 
>SCALAR code only.  

OOOOOOhhhhh, ok, you mean you want permission to ignore Amdahl's law, do you?

Also, I keep trying to get you guys to stop using the word "SCALAR" when
what you really mean is "a small amount of parallelism". This is an
extremly sloppy situation. What if my vector lengths are of length 2? 
Aren't you going to stand by your claim? You will? Then DON'T use the
word SCALAR, please. You mean't so say "no parallelism".

The whole misuse of the terms "SCALAR" and vector on this net just
underlines the lack of understanding about what makes computers slow, or
fast. On the one hand I've got folks trashing on me saying that "box"es
of micros are going to be faster than hell due to all the parallelism
in programs. ON the other hand I've got risc/micro guys saying "well
as long as there is no parallelism, we'll beat a CRAY!". :-) :-)

>
>I certainly agree with you that micros will never compete with the 
>VECTOR performance of these machines simply because the memory
>bandwidth is not going to be available.   

Then how come I have to answer flames that claim the opposite? :-)

>For my large scientific 
>problems (which are >98% vector code), I much prefer the CDC memory-
>to-memory approach.  Having a data cache would be very little help.
>However, Cray and CDC/ETA machines are not likely to ever be cost-
>effective on scalar codes, precisely because most of their budget
>goes into producing huge bandwidth memory subsystems....

However, the ETA machine is fundementally damaged in its ability to
do other than stride 1 accesses. Presumably they will fix this someday.

You may simplify your statement: "Cray and CDC machines are not going
to be cost effective." :-)



    Paul K. Rodman 
    rodman@mfci.uucp