AN/FSQ-7

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AN/FSQ-7 computer. Note the phones located on the end of every cabinet to save time calling in problems.

The AN/FSQ-7 intercept computer, developed by IBM in partnership with the US Air Force. It was used in performing air defense command and control functions for the SAGE air defense system.

The AN/FSQ-7 used 55,000 vacuum tubes, about 1/2 acre (2,000 m²) of floor space, weighed 275 tons and used up to three megawatts of power. The AN/FSQ-7s remain the largest computers ever built, and will likely hold that record in the future. Fifty two computers were built.

The concept was first tested on the Whirlwind I at Cambridge, Massachusetts connected to receive data from a long-range and several short-range radars set up on Cape Cod. The key breakthrough was the development of magnetic core memory that vastly improved the machine's reliability, operating speed (×2), and input speed (×4) over the original Williams tube memory of the Whirlwind I.

After Whirlwind I was completed and running, a design for a larger and faster machine to be called Whirlwind II was begun. But the design soon became too much for MIT's resources. It was decided to shelf the Whirlwind II design without building it and concentrate MIT's resources on the Whirlwind I. IBM, the prime contractor for the AN/FSQ-7 computer based the machine's design more on the stillborn Whirlwind II design than on the original Whirlwind. Thus the AN/FSQ-7 is sometimes incorrectly referred to as "Whirlwind II", even though they were not the same machine or design.

[edit] References

Morton M. Astrahan, John F. Jacobs, History of the Design of the SAGE Computer - The AN/FSQ/7 (Annals of the History of Computing, Vol. 5 (No. 4), 1983, pp. 340-349)