In 1957, IBM began the construction of the Semi-Automatic Ground Environment, by far the world’s largest computer. Spanning more than 20 different locations, each equipped with acre-sized computers and connected by a nation-wide network of bleeding-edge 1,300-baud modems, SAGE was the pinnacle of the United States’ Cold War radar and missile air defenses.
SAGE, like most supercomputers, was built to solve a big data problem. During the Cold War, hundreds of radar installations across North America were constantly on the lookout for Soviet missiles and bombers. As you can imagine, these stations produced a lot of data — a lot of data that needed to be analyzed and acted upon immediately.
With the physical size of the US, the high speed of modern jet aircraft, and the sheer number of possible attack vectors, the US military decided that a network of computers was the only viable solution.
SAGE consisted of 20 or so Direction Centers, each of which was a windowless, one-acre-large concrete cube. Inside each DC were two CPUs, each one measuring 7,500 sq ft and consisting of 60,000 vacuum tubes, 175,000 diodes, 13,000 newfangled transistors, and 256KB of magnetic core RAM, consuming a total of 3MW of power and weighing in at 250 tons. Each CPU — only one operated at a time; the other was kept as a hot spare to minimize downtime — was capable of executing 75,000 instructions per second, which was enough to spit out tons of radar data to 150 CRT consoles.