IBM 727

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An IBM 704 mainframe with IBM 727 tape drives on the left. (image courtesy of LLNL)

The IBM 727 Magnetic Tape Unit was announced for the IBM 701 and IBM 702 on September 25, 1953. It became IBM's standard tape drive for their early vacuum tube era computer systems. Later vacuum tube machines and first-generation transistor computers used the IBM 729-series tape drive. The 727 was withdrawn on May 12, 1971.

The tape had seven parallel tracks, six for data and one to maintain parity. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity. Aluminum strips were glued several feet from the ends of the tape to serve as logical beginning and end of tape markers. Write protection was provided by a removable plastic ring in the back of the tape reel.

tracks	6 Data, 1 parity
chars/inch	200 Chars/inch
Tape speed	75 Inches/sec
Rewind speed	500 Inches/sec (average)
Transfer rate	15,000 Chars/sec
Start time	5 Millisec
Stop time	5 Millisec
Width of tape	1/2 Inches
Length of reel	2,400 Feet
Composition	Mylar or cellulose acetate base

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IBM 727 Magnetic tape unit

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Magnetic tape data storage formats

Three Quarter Inch (19 mm)

Linear

LINCtape (1962) • DECtape (1963)

Helical

Sony DIR (19xx) • Ampex DST (1992)

Half Inch (12.65 mm)

Linear

UNISERVO (1951) • IBM 7 track (1952) • 9 track (1964) • IBM 3480 (1984) • DLT (1984) • IBM 3590 (1995) • T9840 (1998) • IBM 3592 (?) • T9940 (2000) • LTO Ultrium (2000) • T10000 (2006)