Summary

Control Data Corporation Type 604 magnetic tape memory unit. Consists of large cabinet with reel-to-reel tape drive and associated electronics. Used for mass storage of information in the 1960s. Part of CDC 3200 Computer System at Monash University. Made by Control Data in the United States of America about 1962.

This unit is fitted with a vacuum capstan system. This system, powered by a vacuum pump, ensures that the tape passes to and fro past the read/write head at constant speed thus eliminating errors. Provision is made to allow the density of writing on the tape to be set to 200, 556, or 800 characters per inch depending on the accuracy required. Numbers were represented in binary coded decimal format.

The carousel switches at the top of the 604 tape unit allowed operators to change the logical tape unit assignment as opposed to the physical unit. This allowed flexibility in accessing various tape units from application programs. If a program was trying to read or write to logical unit “1” and the tape unit was say faulty or the wrong tape was on it, then the operator could switch to another tape unit and set the switch to “1”. The original tape unit would then be set to some other value other than 1 in the range from 2 to 7 or standby (octal addressing, no 8 or 9). The maximum number of Tape units per controller was 8 addressed as 0 to 7. The 604 tape unit tape speed was 75 inches per second and had a character density of 200 or 556 6 bit + parity Binary Coded Decimal (BCD) characters per inch. Transfer rates were 15 or 41.7 Kilo characters per second respectively.

Physical Description

Cabinet with grey side panels. Two full height grey doors on back. Upper front of cabinet has two tape spindles complete with reels and tape behind vertical sliding glass window. Control panel below window has 12 rectangular push buttons. Rotatable display above window can show numerals 1 to 7 or the words 'STAND BY'.

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