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IBM 2420 magnetic tape unit

IBM 2420 Magnetic Tape Unit

IBM 2420 Magnetic Tape Unit

IBM announced the 2420 in January 1968 as the fastest self-threading magnetic tape unit using standard computer tape. The Model 7 could record or read the equivalent of a 53,000-word book in one second. Nearly twice as fast as previously available standard IBM tape drives, the 2420 was used with most large-scale System/360s, including the then new Model 85.

Information was stored on or read from a half-inch wide tape at a data rate of 320,000 bytes (640,000 digits) a second in the 2420 -- almost as fast as the IBM Hypertape unit (which used a special one-inch computer tape).

A new mechanical concept was incorporated in the tape transport to achieve unprecedented performance levels. For example, to thread tape, all an operator had to do was place a tape reel on the machine's hub and press a button. The 2420 did the rest. It carried the tape on a cushion of air across the read/write head to the take-up reel where the loose end was automatically secured by a vacuum. The entire operation took eight seconds, less than half the time required to thread manually. (Automatic threading is especially important in computer installations where tape reels must be changed frequently.)

Other key features contributing to the 2420's high performance included:

At the time of the announcement the IBM 2420 for use with System/360 Models 50, 65, 75 and 85 rented for $1,050 a month and sold for $54,600. Rental for the 2420's control unit -- which could support up to eight tape drives -- was $1,175 a month, with a purchase price of $55,400.

The 2420 was manufactured at IBM facilities in Boulder, Colo., where it was designed. The first Model 7 production units were installed at Boeing in Seattle in December 1968. Shipments of the Model 5 -- redesigned from the Model 7 for greater ease of manufacturing and service-- began in October 1969.

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