The Largest Computer In The World

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The Largest Computer In The World

h3. How to fight Soviet missiles with punch cards, light wands and the world's biggest computerShortly after the Soviet Union detonated their first atomic bomb, on August 29, 1949, the United States government decided that it needed some technology...

Shortly after the Soviet Union detonated their first atomic bomb, on August 29, 1949, the United States government decided that it needed some technology that didn't exist yet.

The result, completed less than a decade later, was SAGE, short for Semi Automatic Ground Environment, a system that foretold operating systems and the Internet, gave birth to the largest computer ever built, and came in at an estimated total price between $8 and $12 billion, four times the cost of the Manhattan Project.

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SAGE was, like many of our most expensive things, top secret. It featured a network of AN/FSQ-7 computers, a precursor to modern air traffic control systems that was capable of observing, evaluating and communicating incoming airborne threats. To generals, the computer looked like high-tech security. To IBM, then the lion of computing, the project looked like money. While RCA was awarded an original contract, IBM quickly became the top candidate for building the thing.

After consulting with scientists at what would become MIT's defense-focused Lincoln Labs, IBM executives realized they were looking at one of the largest data processing opportunities since the company won the Social Security bid in the mid-1930s. Winning the contract would prove crucial for cementing IBM's domination of the computer industry. But some at the top doubted the wisdom of getting involved in such a complex project. Thomas Watson, Jr., who was then lobbying his father and others at the company to move into the computer market, recalled in his memoirs that he wanted to "pull out all the stops" to be a central player in SAGE. "I worked harder to win that contract than I worked for any other sale in my life."

The dividends would be enormous. Between 1952 and 1955, the computer system generated 80 percent of IBM's revenues from computers, and relied on more than 7000 IBMers. The total cost of the project to the American taxpayer remains unknown, but estimates place it between 8 and 12 billion 1964 dollars, around 55 billion 2000 dollars, which was four times more than the Manhattan Project that developed the bomb which SAGE was intended to stop.

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To build the world's most advanced computer, IBM quickly assigned about 300 full-time employees to the project, mainly at IBM's Poughkeepsie and Kingston, NY facilities and in Cambridge, Massachusetts, home of MIT. While they developed brand new memory systems, MITRE and the Systems Development Corporation (part of RAND Corporation) wrote software; other vendors supplied components.

A SAGE operator at his terminal used a light pen, which was shaped like a handheld power drill or gun, to pinpoint threats on the CRT. The terminal's desk contains a built-in ash tray and cigarette lighter.
A radar station on Cape Cod, Massachusetts
A promotional film for SAGE

The machine's specs included a number of innovations: approximately 24 68K magnetic-core memories, which worked faster and held more data than earlier technologies, and rivaled the RAM of the first personal computers; the first real-time operating system, with overlapping computing and I/O operations, capable of processing about 75,000 instructions per second; real-time transmission of data over telephone lines; the first use of CRT terminals and light pens; and redundancy and backup methods and components, which led to the highest reliability of computer systems of the day. Though the tubes were unreliable, the use of two computers at each site, with one processor kept on "hot standby" at all times, gave the system a remarkably high overall uptime, with around 99% availability, which is on par with Amazon's EC2 servers today.

It was also a giant: with 55,000 vacuum tubes, weighing 275 tons, occupying half an acre of floor space, and using up to three megawatts of power (each came with its own generating and air conditioning plant), the AN/FSQ-7 remains the largest computer ever constructed.

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With its facade covered in hundreds of neon lamps, dozens of incandescent lamps and hundreds of switches, the computer was the epitome of the giant "blinkenlights" mainframe computers of the 1950s and '60s. The lights weren't for show: they allowed engineers to monitor the flow of data through the system, and in maintenance mode, to literally follow the progress of a program through the computer by watching the neon lights.

A section of the building-sized AN/FSQ-7, which featured built-in telephones for maintenance calls.
Robert Duvall and the SAGE computer in "The Time Tunnel" (1967).

Of course, its blikenlights facade would also give the AN/FSQ-7 a life after retirement: as a sci-fi set designer's dream prop. After the first SAGE system was retired in the 1960s, pieces of the system began appearing, in all of their light-blinking glory, on campy sci-fi shows. The computer's dozens of cameos include The Man From U.N.C.L.E., Voyage to the Bottom of the Sea, and an episode of Lost, where it appears inside the Dharma Station. In 1996, ABC even used the computer during election night coverage, to give its set more of a "high tech" feel – again, in 1996.

When the prototype was released in June 1956, it was capable of calculating the most effective use of missiles and aircraft to fend off attack, while providing military commanders with a view of an air battle. By 1963, when it was fully deployed, SAGE included 23 operation centers, each with its own AN/FSQ-7 system; the system would grow to 54 centers in total, each connected to the rest by early modems.

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After the network detected an incoming "blip" from the radar data, a human controller would see the threat as an icon on his CRT radar monitor. Using a "light pen," he would point at the blip, manually feeding back to the computer the information it needed to dispatch interceptors, like missiles and aircraft. Impressively, the system was also designed to connect to a fighter plane's autopilot, allowing the ground operator at the radar scope to use his light pen to actually control the interceptor's speed, heading, and altitude, leaving the pilot to operate the aircraft's radar and weapons system. This silent means of control was called "data link." Today we refer to it as "Internet."

SAGE terminal screen.
A diagram of the SAGE system.
A map of SAGE's radar sites

All told, SAGE was the first geographically distributed, online, real-time application of digital computers in the world. Using what it had learned from the project, IBM excelled as the world's leading designer, manufacturer and manager of complex computer systems for decades. SAGE would remain in service until January 1984, when it was replaced with a next-generation air defense network.

While the network led to advances in online systems, interactive and real-time computing, and modem communications, by the time it was finished, it would prove dumb against the threat for which it was built but couldn't predict: Soviet bombers and intercontinental ballistic missiles.

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A replacement had been a long time coming. From the start of the project, questions lingered about SAGE's usefulness in an actual "hot war" situation. On one occasion, the Strategic Air Command was able to penetrate the system's defenses, and on other occasions huge flocks of seabirds were tracked as a potential bomber attack. By the time the system became fully operational, the USSR had already started deploying ICBMs, which made SAGE largely useless. As an added safety measure, the Air Force also developed the Back Up Interceptor Control System (BUIC), a kind of mini-SAGE located at some of the radar sites that normally fed the SAGE system.

Even if SAGE wasn't fast enough to protect against the more formidable threat of massive bomber and long-range missile attacks, its legacy extends far across computer history. Its most direct legacy however may be the systems IBM began developing near the end of the SAGE project: the national air traffic control system and SABRE system, which is still the world's central travel reservations network.

Keep that in mind the next time you contemplate the trajectory of technology, or fly: the computer systems that puts airplanes in the sky now grew out of one intended to take them down.