Path: utzoo!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!shadooby!ginosko!uunet!dg!daver
From: daver@dg.dg.com (Dave Rudolph)
Newsgroups: comp.arch
Subject: Re: parallel systems
Message-ID: <224@dg.dg.com>
Date: 25 Oct 89 13:29:32 GMT
References: <20764@usc.edu> <36662@lll-winken.LLNL.GOV>
Reply-To: uunet!dg!daver (David Rudolph)
Organization: Data General, Westboro, MA.
Lines: 12

In article <36662@lll-winken.LLNL.GOV> brooks@maddog.llnl.gov (Eugene Brooks) writes:
>In article <20764@usc.edu> vorbrueg@bufo.usc.edu (Jan Vorbrueggen) writes:
>>Message forwarding isn't so difficult either. I've read of a system
>>requiring less than 10 us overhead per through-route (this probably
>>is for the destination link being available). No interrupt handling
>>involved here - that part is all handled in hardware.
>This level of overhead for each hop is completely intolerable.

And what is the overhead for each interconnect level in a "shared
memory" machine such as the ultracomputer?  Keep in mind that in such a
machine, every non-local memory access must go through each level and 
back while the processor waits.