Seymour Cray: An Appreciation

Toby Howard

This article first appeared in Personal Computer World magazine, February 1997.

SEYMOUR CRAY, the father of the supercomputer, died recently aged 71, following a car crash. He was one of the most original computer designers the world has ever seen, and a true maverick. Seeking a way to cool the machine he built in 1985, at the time the fastest computer in the world, he characteristically chose to immerse it in artificial blood.

Although never a household name, Seymour Cray was a legendary figure in the computing world. His designs for supercomputers were ingenious to the point of miraculous, and the machines he designed and built were, for much of the 60s, 70s and 80s, the most powerful -- and the most expensive -- on the planet.

Cray was born in 1925, in Chippewa Falls, Wisconsin, and from an early age was fascinated with radios, motors and electrical circuits. After a spell in the US Army, he graduated with a Bachelor's degree in electrical engineering, and a Master's in applied mathematics.

At his University intructor's suggestion, Cray went to work at a small company building specialised cryptographic equipment for the US Navy. The unlikely home of the company was a converted factory for manufacturing wooden gliders.

It was here that Cray designed his first computer, the 1103. "My guiding principle was simplicity", he said, and throughout his career this remained the focus of his design philosophy. He was building RISC machines long before IBM coined the term in the 1970s.

In 1957, Cray and some others left to start Control Data Corporation, and it was here that Cray designed the 1604, one of the world's first fully-transistorised computers. The age of the vacuum tube was over.

He soon became chief architect of the 6600 machine, released in 1963 and regarded by many as the world's first true supercomputer, offering 9 Mflops (million floating-point operations per second) of processing power. The 6600 far outstripped IBM's 7094, until then the fastest machine available, and IBM were understandably upset. There is an apochryphal story that IBM chairman Thomas J Watson berated his staff with a memo asking how it was possible that giant IBM could possibly be outdone by tiny CDC, whose workforce numbered only 34, "including the janitor".

At CDC, Cray's legendary dislike of bureaucracy soon became apparent. Asked to write a five-year plan for the company, his response was: "Five year goal: Build the biggest computer in the world. One-year goal: Achieve one-fifth of the above".

CDC maintained their world lead with the 7600, also designed by Cray, running at 40 Mflops. In 1971 Cray broke to form his own company, and produced the Cray-1 in 1976. Now using integrated circuits in place of transistors, the Cray-1 delivered 170 Mflops. The first Cray-1 was sold to Los Alamos National Laboratory, for nearly $9 million. Sixteen more were subsequently sold, into the scientific number-crunching and intelligence markets.

Because of his insistence on using the latest technologies, which were sometimes not mature enough for the job, some of Cray's designs ran into trouble. For his next machine, the Cray-2, he intended to shift from the usual silicon chips to faster, but unproven, gallium arsenide technology. Manufacturing difficulties forced him back to silicon, and the Cray-2 arrived, delayed, in 1985. Nevertheless, it broke the giga-flop (one thousand Mflops) barrier. This was the machine that was cooled by being completely immersed in an inert fluorocarbon liquid, the same liquid used as artificial human blood. Ever stylish, Cray included a decorative fountain in the coolant circulation system.

As soon as one machine was completed, Cray would begin on the next, which was to be bigger, better and faster. There was a story that each spring he would build a sailboat to sail on the lake near his home, then burn it in the fall.

Cray's last completed machine was the Cray-3, of which only one demonstration model was ever built. After the only customer backed out, the machine, worth $30 million, was given free to the National Centre for Atmospheric Research in Boulder.

All through his career, fellow engineers marvelled at Cray's uncanny ability to hold every tiny detail of a computer design in his head. One story has it that Cray was called in to fix a baffling problem with a Cray-2. He locked himself in the machine room and after contemplating for 6 hours, eventually called an engineer. Cray pointed to a single wire and asked for it to be replaced. The machine worked again.

In 1995, Cray's company ran into financial trouble, and the planned Cray-4 machine was never completed. In the months before his death, at his new start-up company, SRC Computer Inc, Cray was working on a new supercomputer called the SRC-6.

There are many legends about Seymour Cray. John Rollwagen, a colleague for many years, tells the story of a French scientist who visited Cray's home in Chippewa Falls. Asked what were the secrets of his success, Cray said "Well, we have elves here, and they help me". Cray subsequently showed his visitor a tunnel he had built under his house, explaining that when he reached an impasse in his computer design, he would retire to the tunnel to dig. "While I'm digging in the tunnel, the elves will often come to me with solutions to my problem", he said.

Cray has been called solitary, uncommunicative, secretive, and difficult to get on with. Frank Sumner, Professor of Computer Engineering at the University of Manchester, met Cray on several occasions and refutes suggestions that he was a prickly character: "He was a very friendly man, and perhaps the greatest all-round computer scientist ever", says Sumner.

Although Cray said of himself in an interview with the Smithsonian Institute in May 1995, "I was one of those nerds before the name was popular", he will be fondly remembered as the father of the supercomputer, a man whose genius changed the world.

Toby Howard teaches at the University of Manchester.