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Path: utzoo!utcs!lsuc!mnetor!mot!fred
From: fred@mot.UUCP (Fred Christiansen)
Newsgroups: net.micro.68k,net.arch
Subject: Re: Re: Multiple 68020's on VME ?
Message-ID: <343@mot.UUCP>
Date: Fri, 4-Oct-85 14:19:10 EDT
Article-I.D.: mot.343
Posted: Fri Oct  4 14:19:10 1985
Date-Received: Sat, 5-Oct-85 04:38:55 EDT
References: <442@rna.UUCP> <552@spar.UUCP>
Organization: Motorola Microsystems, Tempe, AZ  85282
Lines: 21
Xref: utcs net.micro.68k:1197 net.arch:1845

> The August 1, 1985 issue of Computer Design contains a rather interesting
> article on metastability problems in multiprocessor VME systems.  It appears
> to be a little trickier than expected to design VME bus and memory arbitration
> logic that is not vulnerable to metastability problems in synchronization.  In
> particular, some folks at CMU's robotics lab discovered that "as few as two"
> 8-MHz Motorola VM02 68000 boards would lock up "within 4 to 10 minutes".
> 
> 						Baba ROM DOS

I read the article a found the line of reasoning a little weak in places.
VME was being blamed, yet the example cited used VM02 boards which are Versabus
not VMEbus based.  So, I dropped in on a hardware sharpie and asked what the
scoop really was.  The gist of his statement was that the problem was one
found in all the popular busses, although more particularly the asynch busses.
HW designers are aware of the problem and have been successful in working
around it.
-- 
<< Generic disclaimer >>
Fred Christiansen ("Canajun, eh?") @ Motorola Microsystems, Tempe, AZ
UUCP:  {seismo!terak, trwrb!flkvax, utzoo!mnetor, ihnp4!btlunix}!mot!fred
ARPA:  oakhill!mot!fred@ut-sally.ARPA             Telephone:  +1 602-438-3472


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