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From: frazier@CS.UCLA.EDU
Newsgroups: comp.arch
Subject: Re: Coprocessors
Message-ID: <8699@shemp.UCLA.EDU>
Date: Sun, 18-Oct-87 21:22:32 EDT
Article-I.D.: shemp.8699
Posted: Sun Oct 18 21:22:32 1987
Date-Received: Tue, 20-Oct-87 00:43:03 EDT
References: <185@PT.CS.CMU.EDU> <2390@umn-cs.UUCP>
Sender: root@CS.UCLA.EDU
Reply-To: frazier@CS.UCLA.EDU (Greg Frazier)
Organization: UCLA Computer Science Department
Lines: 28
Keywords: Coprocessors

>I define coprocessors as general purpose processors assigned to perform
>specific tasks in parallel with the main processor.
>-- 
>  Neta Amit 
>  U of Minnesota CSci
>  Arpanet: amit@umn-cs.cs.umn.edu

Then what is the difference between a processor/coprocessor pair and
two independent processors operating in parallel?  I would define a
coprocessor as a special purpose processor which either receives
instructions from the "main" processor(s) or shares the main processor's
instruction stream, but only executes "special" instructions (i.e.
floating point coprocessors sample the instruction stream, operating
only on the floating point operations).  Thus, the difference between
a coprocessor and an IO processor is that the IO processor is not
involved in the instruction stream, but has it's own code for dealing
with I/O which is independent of the code currently being executed by
the "main" processor(s).

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Greg Frazier              Your feet are frozen to the floor...  -more-
CS dept., UCLA

Internet: frazier@CS.UCLA.EDU
    UUCP: ...!{ihnp4,ucbvax,sdcrdcf,trwspp,randvax,ism780}!ucla-cs!frazier

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