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From: eugene@ames.UUCP (Eugene Miya)
Newsgroups: net.arch
Subject: Re: Re: Caltech's Cosmic Cube
Message-ID: <807@ames.UUCP>
Date: Wed, 20-Feb-85 14:32:26 EST
Article-I.D.: ames.807
Posted: Wed Feb 20 14:32:26 1985
Date-Received: Fri, 22-Feb-85 14:30:39 EST
References: <333@oakhill.UUCP> <21294@lanl.ARPA>, <7268@watrose.UUCP>
Organization: NASA-Ames Research Center, Mtn. View, CA
Lines: 39

<166@cmu-cs-wb1.ARPA>

> This Cosmic Cube is really puzzling me... 
> 
> What puzzles me is why use point to point channels between processors (and
> do routing if a connection does not exist)?  Wouldn't it be much simpler to
> use a dedicated ethernet?  A 10mb ethernet should easily provide the
> necessary bandwidth for 64 or more processors.  Since the ethernet would be
> dedicated, minimal protocols could be used, thus keeping the costs of
> managing the ethernet down.  If 10mb is not enough bandwidth (which I highly
> doubt), it shouldn't be too tough to increase the bandwidth considering that
> the wire will be dedicated and can be very short (it won't need to run all
> around a building).
> 
> 	Avie Tevanian

to this and other articles about the Cube and the new Intel cube:  the
new intel cube does use ethernet controller chips for point to point
communication [Justin Rattner, at Ames last week]. don't forget these are
research machines and multiprocessor comunications is one area of research.
the intel machine also has an extra 'global' ethernet for passing
interrupts and the like.

communications and massive memory are major problems with supercomputers.
our cray sends 1.2 GB/sec to a solid state storage device.
big bandwidth is a long term problem since you don't want your processors
waiting very long, nor do you want big buffers for i/o, you don't
want your processors calculating ethernet backoff after a collision
has been detected.

these machines are not cray replacements.  big mainframe 308x machines
outperform these cubes [cube i/o is especially poor].  tech's cube has
i/o thru a single pe, intel has proposed cray-like disk stripping
with disks off every pe.

--eugene miya
  NASA Ames Research Center
  {hplabs,ihnp4,dual,hao,vortex}!ames!aurora!eugene
  emiya@ames-vmsb.ARPA