In His Element

To describe Cray as a recluse is going too far but some might have seen him as such - but this is would simply be a misunderstanding of another's paradise! Even so Cray's behaviour must have seemed very odd to the non-techie CDC executives. They would drop in on Cray and be whisked off to the local diner where he would eat a hot dog and vanish as soon as possible back to the lab.

It was said that his method of working was to grab some chips and a soldering iron and put his latest idea together on a card table. I doubt it, but it might have looked like that! The clue to how Cray really worked is the fact that he used a whole pad of paper every day. The pad was covered by design ideas which was passed on to his team of technicians who produced finished electronics.

In 1963 the 6600 was finished and it was the most powerful computer ever built. It was priced at $7.5 million and they eventually sold over fifty. At first, however, there were problems. The 350,000 transistor machine needed debugging and this took time. The first machine was six months late and it still had bugs.

The Cray 6600

Cray Research

Cray went ahead with the design of the 7600 and the 8600 but CDC decided not to market the 8600 and so Cray became unhappy yet again.

CDC had become a power in the business computing field and they downgraded the work on supercomputers. This time Cray really did have to go it alone. He left CDC and formed Cray Research - dedicated to supercomputers. The leaving wasn't acrimonious, CDC contributed $500,000 to the startup and they promised not to build any more supercomputers.

The design Cray had in mind was revolutionary and would eventually make money - but at first it was a struggle. Cray Research was set up in 1972. By 1976 the money had run out and the Cray 1 still wasn't ready.

The solution to the problem was to go public but Cray Research was a company that didn't have a product and it did have a $2.5 million deficit. Amazingly Wall Street came up with the funding - $10 million almost immediately - the word about Seymour Cray must have leaked out.

Cray would work with his team for a few hours and then go home at around 4pm - but he would return at night to work alone at the late shift. An eccentric genius who surely must be worth a few dollars gamble.

Photograph courtesy of the Charles Babbage Institute, University of Minnesota, Minneapolis

The first Cray-1 was delivered to Los Alamos Lab in March 1976 at a cost of $8.8 million. There were thought to be only eight potential customers for the Cray-1. By 1980 it had sold nine, thirteen more in 1981, and fifteen more in 1982. Not a mass market product but it made the company a great deal of cash which more than repaid the investment.

Speed Counts

The reason that people wanted the machines was simple - it was the fastest machine available. By using a vector processor it could perform the sort of arithmetic needed to solve many scientific problems.A whole set of numbers could be multiplied in a single operation.

As well as being a fast vector processor the Cray-1 was also the fastest scalar processor of its time. Its cycle time of 12.5ns was equivalent to a clock rate of 80MHz. The only real competitor to the Cray-1 was the CDC Cyber 205 which worked at only 40MHz. Yes, that's right, CDC did not keep its promise to stay out of the supercomputer market.

Although these clock rates are not high by today's standards you have to take into account the fact that the machines were built of individual bipolar logic chips. This results in parts of the machine that would be next to each other on a single chip using today's large scale integration were separated by large distances on printed circuit boards. In this case the transmission time for a pulse is an important factor in how fast a machine can work. Pulses cannot travel faster than light - around 1 foot per nanosecond - and in practice they usually propagate at closer to .3 to .9 feet per nanosecond.

The Cray 1 achieved its higher clock rate by being smaller and packing 300,000 chips into less than 100 cubic feet. To get rid of the heat the whole machine had to be cooled by a Freon refrigerant - something Cray pioneered in his days with CDC. Each circuit board was bonded to a sheet of copper and which slid into massive vertical slabs of aluminium in which the Freon circulated.

The machine was also built into a semi-circular case with what looked like seats around the base. The horseshoe shape kept the connections from one part of the machine to another short and the "seats" were in fact the power supplies. Even if the design was functional there is no denying that it looked good and it is still instantly recognisable as the archetypal supercomputer.

The difficulties in building the machine must have been huge. With over 300,000 wire interconnections, each trimmed to an exact length so as to produce a fixed travel time for the pulses, which ran between 1,600 circuit boards, it must have been a wireman's nightmare.

Although it is interesting to know what the clock rates were, it is important to realise that the actual speed of computation had more to do with the overall design of the machine. As well as a single high speed processor, the Cray 1 also had a high speed vector processor which could perform more than one operation at a time. Although it is difficult to be precise about the power of the Cray-1. claiming a top speed of 100Mflops (i.e. 100 million floating point operations per second) is reasonable.