SEYMOUR & NSA REVIVE SIMD AS THINKING MACHINES BURIED
News Analysis by Norris Parker Smith, Editor at Large
High-performance computing is still capable of a few surprises. The
recent termination of Thinking Machines Corp., which had long been
anticipated by industry observers, does not qualify as a real surprise.
The same observers would not have been surprised if the next company to
declaim the hymns of Chapter 11 had been Cray Computer.
After all, the company had yet to sell any of its products. Even though
additional money had been lured from various sources (including the pockets
of founder Seymour Cray), it was presumed that the cash would run out soon.
Seymour Cray is, however, an expert stage-manager, and surprises are one
of his specialties. He has not quite sold a machine, but the National
Security Agency (NSA) will pay Cray Computer $4.2 million to develop an
unusual hybrid system -- half-vector, half-SIMD.
It is anticipated that the new product, the CRAY-3/SSS (for Super
Scalable System) will be demonstrated during the first quarter of 1995.
This particular surprise may not be sufficient to rescue Cray Computer
over the long term, but it certainly enhances the credibility of the
company -- along with the standing of its products and its founder.
STRIKE WHILE THE IRONY IS HOT
An additional irony is provided by the coincidence between this
announcement and the interment of Thinking Machines. From its earliest
years, Thinking Machines and its technofounder, Danny Hillis, were tireless
advocates of the virtues of systems based upon very large numbers of
minimalist processors (about as smart as a primitive digital watch) with
distributed memories, operating in a SIMD mode.
In contrast, Seymour Cray achieved fame (and made his fortune) deploying
small numbers of very powerful proprietary processors sharing a single
memory through a complex, highly sophisticated switch.
Hillis became a heretic in 1991. Thinking Machines revealed the
abandonment of the SIMD/many-tiny-fingers philosophy. They joined the
mainstream religion of somewhat smaller numbers (up to a few thousand) of
powerful commodity microprocessors.
Did this apostasy lead to Thinking Machines' recent doom? This writer is
not licensed to consider cases of moral retribution.
It seems clear, however, that Thinking Machines as a company found it
difficult to manage a mid-stream switch between two very different
architectural horses. Indeed, they had to re-shoe the horses in mid-stream
because, among other things, the old and new products had different
It was also difficult for customers who had to adjust their applications
from the requirements of one product to quite a different one.
THE OLD ORIGINAL MPP
Under Cray's new contract with NSA, a two-processor CRAY-3 vector system
will be joined in computational matrimony with a system that emphatically
deserves the almost-outdated term "massively parallel".
The CRAY-3's partner is to be a SIMD system with 512,000 processors. This
is eight times as many processors as the most massive parallel processor
ever available for general purchase: the 64,000-processor CM-1 and CM-2
SIMD systems sold by Thinking Machines in the 1980s.
It is somewhat reminiscent of the first Massively Parallel Processor
(that was its real name) built by Goodyear Aerospace Corporation and
installed at NASA's Goddard Space Flight Center in Greenbelt, Maryland in
1983. This was a specialized machine used primarily for image processing
with 16,3845 processors. Each was supplied with 1024 bits of local memory.
A Cray Computer announcement says that the microprocessor to be used,
known as a Processor-in-Memory (PIM) chip, was developed by the
Supercomputer Research Center, an affiliate of the NSA.
As on the Thinking Machines CM-2, these are single-bit processors. 64
processors are accommodated on a single slice of silicon, along with 128
kilobits of memory.
Thus the Cray/NSA hybrid of the 1990s will have only twice the memory per
node of the 1983 Goddard/Goodyear machine.
The Goddard/Goodyear MPP system was front-ended by a PDP and a VAX that
loaded application programs, looked after I/O, and carried out the other
functions that parallel systems of that era were unable to perform on their
Will the CRAY-3 simply be doing the job that was once done by a humble
PDP? Not quite. The Cray Computer announcement explains that the "scalable
array will connect to the CRAY-3 memory interface and will be addressable
as standard memory to facilitate use of the SIMD array with minimal delays
for data transfer."
The NSA project will utilize Seymour Cray's exceptional skills in
packaging technology as well as the power of the CRAY-3 which, at a clock
speed of 2.08 ns, is a tad swifter than its closest Japanese competitors.
PIM chips will be packed by Cray using the company's MCM (multiple chip
Once the current Cray-NSA development project is completed, the PIM
chip-based system is said to be able to scale up to one million processors.
Does this signify a general rebirth of SIMD as a widely used, general
purpose architecture for parallel systems?
This question is answered by a sentence in the Cray Computer release:
"The CRAY-3 memory interface bandwidth will allow the application-specific
SIMD array to provide dramatic performance improvements over existing
architectures for bit and image processing, pattern recognition, signal
processing, and sophisticated graphics applications."
That sounds good, but this is just about the complete list of
applications that do well (sometimes spectacularly so) on SIMD
architectures. MIMD architectures, deafened by the din of message-passing
among their distributed-memory nodes, have their own problems.
Nevertheless, MIMD systems (if supplied with good compilers and a great
deal of memory) are able to perform somewhere on a range from adequate to
excellent on a wide range of applications, including many of those that
consume most of the cycles used in high-performance computing.
Since the apostasy of Thinking Machines in 1991, MasPar has been the only
company producing SIMD systems for the general market. (Somewhat like the
NSA strategy, MasPar packages multiple small processors with associated
memory on integrated chips.)
After undergoing a financial health/business-focus/leadership crisis
analogous to the problems that Thinking Machines seemed unable to overcome,
MasPar has changed bosses and slimmed down its staff roster.
In particular, MasPar has stopped trying to sell to everybody and has
focused upon areas like gene research and statistical analysis where a SIMD
architecture, properly equipped with an awful lot of I/O and fast disks to
bounce around a great deal of data, offers distinct price/performance over
conventional MIMD parallel systems or other solutions.
Some of its greatest successes have been in the high-speed comparison and
matching of the strings of letters that biologists use to identify the DNA
makeup of each individual gene.
Who else needs to make high-speed comparisons and matchings of strings of
letters? NSA, for one. That is pretty close to a job description of a
computer optimized for cryptographic analysis.
NSA technologists have been grumping for some time about the present and
anticipated shortcomings of current computers. (Indeed, the Supercomputing
Research Center was formed in an attempt to cope more effectively with this
Meanwhile, the agency's tasks grow more complicated. The cold war may be
over, but other changes are taking place. Sophisticated cryptographic
systems have become simpler, cheaper, and are more widely used -- by
private persons from banks to cocaine wholesalers as well as governments.
In addition, the volumes and speeds of data transmission are growing very
rapidly, making it more difficult to identify significant items and pluck
them out of the message stream.
Along with the rest of the defense establishment, NSA has been under
pressure to cut costs. Buying $25 million supercomputers in half-dozen lots
is not as easy to justify as it once was.
Development of the CRAY-3/SSS is to cost a relatively moderate $9.2
million, divided roughly equally between the NSA and Cray Computer. The
government is also to provide software consulting services valued at about
A new era demands new solutions -- or, in this case, sweeping adaptation
of an old solution.
For Seymour Cray, from his early triumphs at Control Data through his
years at Cray Research, the NSA has always been one of the earliest and
best customers for his supercomputers.
Now that both Cray Computer and the NSA need help, what would be more
plausible than for the two old friends to work it out together?
Right up to the end, Thinking Machines sought frantically to secure
comparable help from one of its old friends, but nothing could be worked
out in time.
SIMD or MIMD, the line can be very fine between failure and managing to
keep on getting by.
These developments are not likely to stimulate vendors of MIMD systems to
comb the lists of former SIMD specialists, cut in the most recent round of
down-sizing and think about calling them back briefly for a consultation.
The CRAY-3/SSS could be a good solution for NSA, but -- with the partial
exception of image analysis -- the real growth in high-performance
computing is taking place in applications categories where SIMD offers no