1979 review of Cray-1 Supercomputer

Another Modern Mechanix post, this one a 1979 Popular Science review of the Cray-1 Supercomputer.  This little speed demon runs along throwing down roughly 80 million operations per second.

Incredible Cray-1 cruises at 80 million operations a second

It’s 10 times faster than the biggest IBM, with six times more memory

. . .

This was the CRAY-1, the amazing supercomputer designed by a reclusive Wisconsin genius. It’s 10 times faster than the biggest IBM computer on the market. And this particular CRAY-1, installed in a major computer center in Kansas City, was being fed by two giant Control Data computers just to keep it busy.

“You’re looking at the architecture of Seymour Cray,” said a voice floating over the top of the computer.

The voice belonged to Jack Lorenz, president of United Computer Systems and owner of the first commercially installed CRAY-1 system. I saw what he meant. The CRAY-1 is unique, not only in electronic architecture and performance, but in size and shape as well. It doesn’t look like any other computer.

. . .

Standing in the CRAY-l’s chilly center—it’s one of the few computers with built-in refrigeration—I was struck by the wiring. Each of the 12 vertical panels was a thick, solid mass of blue and gray wires. There is no color coding in the CRAY-1. How does one tell the wires apart? One doesn’t.

“It’s designed and built on a from-and-to wire list,” I was told later by engineer Lee Higbie at the headquarters of Cray Research, Inc., in Minneapolis. “First we do all the one-foot wires, then all the two-footers, then the three-footers. There are only a couple of four-footers in the entire unit.”

The CRAY-1 is fast. It will cruise along at 80 MFLOPS. That’s 80 million floating-point operations (such as addition or multiplication) per second. With some computations, there’s an overlap that pushes its speed to 140 MFLOPS. And in short bursts, the CRAY-1 has been clocked at 250 MFLOPS.

By comparison, a Cyber 176 or an IBM 360/195-each superfast by former standards—chugs through its duties at four to seven MFLOPS or less.

That’s why it takes “front-ending,” putting another computer on line as an input-output device, to get efficient use from a CRAY-1. Even then, the supercomputer has time to rest.

“Routine jobs go through the Cray with a ‘blip,’ ” Lorenz told me. “It accepts, executes, and completes them as fast as you can feed it. But the real measure of performance is on the tough jobs, like structural or reservoir analysis, or oil-exploration model-ing.”

Such jobs require a computer to run lengthy batches of similar calculations, each only slightly different from the last, until the best possible solution is found.

“We’ve had jobs come in that ran 24 hours on a 6600,” Lorenz explained. “That same job would run two hours on the CRAY-1.”

. . .

In the CRAY-1, simplicity means a design with only three kinds of integrated circuit chips—one for memory, one for logic, and one for internal register. The finished machine contains more than 350,000 chips. But it’s the way they’re put together that makes the CRAY-1 a supercomputer.

One major limiting factor in computer operations is the speed at which a signal travels through connecting wires. The longer the wire, the longer it takes for a computer “message” to get through. And a signal that must work its way through a wire maze in a computer filling a 12-foot cabinet will take longer than a signal zipping around in the CRAY-l’s five-foot polyhedron.

Cray reasoned that a circular cabinet offered the best way to keep wire lengths to a minimum. He flanked the computer’s central processing unit (CPU)—its logic, or brain—with banks of memory chips.

“It’s really a CPU bathed in memory,” Higbie said with the understatement of an engineer grown accustomed to thinking in supercomputer superlatives. “But it’s only a moderate-sized memory, say about the size of a half dozen IBM 360’s’

Cray’s concept for the computer cabinet also yielded the densest packing structure for the thousands of circuit boards filling each machine. Rather than individual boards as in conventional computers, Cray sandwiches groups of them together to form plug-in modules.

. . .

The CRAY-1 draws 100 kilowatts of electricity, more than any other commercial computer. In comparison, astronauts operated the Skylab space station on less than 10 kilowatts. A typical home may draw six kilowatts at peak moments.

With each circuit board generating heat, Cray knew that a new cooling scheme was needed. The air-conditioned coolness of normal computer centers wouldn’t do for his machine. That led to the middle layer of Cray’s five-layer module, and to some unique plumbing in the computer framework.

“The midsheet in the circuit module is heavy copper with a Teflon coating,” Higbie said. “It’s both an electrical insulator and a heat conductor.”

The copper sheet’s edges are left bare. When the module is installed in the chassis, those edges fit into the notches of an aluminum cold plate. Within the cold plate are stainless-steel tubes carrying Freon refrigerant. The refrigerator unit itself is in the floor below the computer.

The constant flow of Freon draws heat away so rapidly that the CRAY-1 is actually cooler than its air-conditioned surroundings, though it may warm up in prolonged operation. That accounts for the sudden chill I felt when I first stepped into the machine.

“We could have installed the CRAY-1 anywhere,” Jack Lorenz of UCS told me. “It doesn’t require the air-conditioned environment that the rest of our machines need.”

All this and more can be found in Popular Science magazine.  And if you were thinking of buying one of these fancy high-speed computers, expect to pay around $8 million.  And it comes with freon cooling, so you won’t need a room sized air-conditioner for it.

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