Re: SSS attachment - is that Splash II?

[nobody@kaiwan.com (Anonymous)]

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Date: Fri, 19 Aug 1994 13:30:42 -0400 (EDT)
From: Ronald G Minnich <rminnich@descartes.super.org>
Subject: Re: SSS attachment - is that Splash II?

The WSJ article on the Cray-3 deal involves a chip/system designed here
called TeraSys. Maya [Minnich djf] has a forthcoming article in IEEE
Computer about it.
The basic idea is to embed bit-serial processors in the sram chips, one
processor per bit in the memory row register. It's a simple processor with
an ALU and three registers. The memory "words" can now be thought of as
running vertically up the columns, rather than horizontally along the
rows. Every time you fetch a row, you are in fact fetching 64 bits from 64
different words to be operated on in the ALUs.This gives you roughly a
100-fold increase in memory bandwidth, since you no longer mux the data
down from 64 bits to 1 or 4 bits to bring it off-chip. The key
contribution of the Cray (this idea due to Ken Iobst of SRC, who also was
the architect of the chips) came from Ken's realization that the Cray vector
scatter/gather hardware could push the bits around BETWEEN the chips as
fast as the hardware networks on, e.g., the CM-2. Thus the Cray-3, a
vector supercomputer, can function as a very high-performance SIMD system
as well. You don't need to build the additional network found on so many
SIMD machines, e.g. maspar or cm-2.  You also can have phases of a
program, wherein it runs SIMD for a while, then vector, then SMP mode,
etc.

The TeraSys processors built here at src cost about $80K each, and for
several problems could easily outrun our $6M CM-2.

The chips are National Semi SRAMS, with mods done here by Mark Norder and
Jennifer Schrader. Ken Iobst is the architect of the chips. The
programming environment was basically Maya Gokhale's DBC language, which
also runs on Splash-2, the CM-2, and clusters. Cray has reimplemented the
chips for the Cray-3.

In keeping with the NSAs new plans for SRC, this project was terminated
at SRC last January. The systems are gradually being turned off and the
cabinets put to other uses. No further work is occurring at SRC in this
area.

Feel free to forward this article to people who may ask you. There was
some good work done by people here.

ron

rminnich@super.org     | Error message of the week:
(301)-805-7451 or 7312 | NFS server localhost not responding still trying

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