IBM 727 Magnetic Tape Unit
Tape Data Recovery - IBM 727 Magnetic Tape Unit
IBM 727 Magnetic Tape Unit was the standard tape drive for the earlier vacuum tube era computers of IBM. It was first introduced in the IBM 701 and IBM702 in 1953. Later IBM introduced IBM 729 series tape drives, which were used for both vacuum tube machines and the first generation transistor computers. IBM 727 was withdrawn in 1971.
IBM 727 Magnetic Tape Unit provided large capacity storage for programs and data. It provided intermediate speed, but was also used as a high-speed input unit for information previously recorded on magnetic tape.
Architecture
IBM 727 Magnetic Tape Unit consists of seven parallel tracks – six for data and one to maintain parity. Tapes with character data are recorded in even parity while binary tapes used odd parity. To mark the logical beginning and end, a small aluminum strip was glued a few feet away from the ends of the tape. A removable plastic ring provided in the back of the tape reel enabled write protection feature.
The tape had a recording density of 200 bits per linear inch. It could be read in a forward direction or back-spaced at the rate of 75 inches per second. Rewind speed was 500 inches per second. Data transfer rate was 15,000 characters a second.
IBM 727 could transfer data from a punched card to magnetic tape by connecting to an IBM 714 Card Reader and an IBM 759 Card Reader Control Unit. Recording speed was 250 cards a minute. To transfer data from tape to cards, an IBM 722 Card Reader and an IBM 758 Card Punch Control Unit were connected to the IBM 727.The speed to punch records of 80 characters or less was 100 cards per minute.
To transfer data from tape to print, the unit was connected with IBM 717 Printer and IBM 757 Printer Control Unit. Printing speed was 150 lines per minute.
