Magnetic Core Memory Patented

Today in 1956, Jay Forrester of MIT was awarded a patent for his magnetic core memory. It became the standard for computer memory until it was supplanted by solid state RAM in the mid-seventies. It has continued to be used, however, in special environments (e.g., on the space shuttle), because its content was not lost when the power was shut off.

Forrester came up with the idea of 3D storage of computer data while working on MIT’s Whirlwind computer, which required a fast memory system for real-time aircraft tracking. In an interview for the 150th anniversary of MIT last year, Forrester explained the background for inventing a new kind of computer memory in the late 1940s:

“…it was a clear case of necessity being themother of invention. I had a group 200 or 300 engineers building a system that we knew wasn’t going to be reliable enough with essentially a commitment to military reliable equipment. What we were building or what we had operating was clearly not sufficient. The electrostatic storage tubes that we had designed here, I think they were perhaps better than what was otherwise being used at the time, but it cost about $1,000 to make one. They stored about 1,000 binary bits. They lasted about a month. We were paying about $1 per month per binary bit to maintain storage. If you take your 500 megabyte computer that’s $500,000 a month to maintain it.”

Forrester’s was not the only patent granted to magnetic core memory inventions and the patent dispute continued until February 1964 when IBM (which has acquired the patent rights from other inventors, including An Wang) agreed to pay MIT $13 million—$4 more than had ever been paid to secure a patent—of which Forrester received $1.5 million. Forrester succinctly described the experience many years afterwards: “It took about seven years to convince people in the industry that magnetic core memory would work. And it took the next seven years to convince them that they had not all thought of it first.” [quoted in Memory and Storage, Time-Life Books, 1990]

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