Newsgroups: comp.parallel
From: gmcghee%kgserv1mach@relay.nswc.navy.mil (Greg McGhee)
Subject: Re: Symmetric Multiprocessing
Organization: Naval Surface Warfare Center - Dahlgren Div.
Date: 21 Dec 1995 05:12:08 GMT
Message-ID: <1995Dec14.215717.16454@relay.nswc.navy.mil>

In article <DJ7oGp.ABC@hkuxb.hku.hk>, Starry Hung <kphung@hkuxa.hku.hk> writes:
|> 
|> 
|> I read the definition of symmetic multiprocessing from the book of Curt
|> Schimmel, "Unix System for modern architectures"  Symmetric multiprocessing
|> and caching for kernel programmers".  He said that symmetric means that all
|> CPUs and I/O devices have equal access to the global shared memory.
|> 
|> >From that on, I think symmetric multiprocessor is more or less the same
|> as uniform memory access multiprocessor as frequently discussed in academic
|> some years ago.  
|> 
|> Like to see your postings about this commonly talked, but less explained,
|> jargon in multiprocessor industry.
|> 
|> 
|> Starry.
|> 

Greg Pfister has also provided a similar definition in his book "In Search of
Clusters".  Mr. Pfister goes further to suggest that all processors have equal
access to all system resources.  This adds an additional constraint to the
symmetry.

Another way to look at this (in my opinion) might be as follows.  A symmetric
multi-processor could be defined as symmetric in every way, shape, and form.  
That is, all processors in the system are identical, they have identical access 
to all system resources, etc.  Any perturbation to that symmetry will result in 
an asymmetric multiprocessor.  Therefore, if one has a multiprocessor system
that consists of multiple CPU types, that system could be defined as asymmetric.

While multiple CPU types are not prevalent in the commercial world, We in fact
have a system which meets these attributes in the Military Standard
UYK-43 computer.  This is a 4 processor system in which two like CPUs are
dedicated to "application" processing while another set of unlike CPUs are
relegated to the handling of I/O.  Of course, we write and maintain our own
operating systems for this computer.

Regards,

Greg

=============== Please make note of the area code change =====================
+ Gregeory A. McGhee (Greg)             +  Computer Sciences Corporation     +
+ Senior Member of the Technical Staff  +  Oak Manor Office Park, Suite 201  +
+ E-Mail:  gmcghee@mach.nswc.navy.mil   +  5166 Potomac Drive                +
+ (540)663-9251                         +  King George, Virginia  22485-5824 +
+ (540)663-3990 FAX                     +                                    +
======================= Usual Disclaimers Apply ==============================


