IBM 729 Tape Unit

The IBM 729 magnetic tape unit used 1/2 inch magnetic tape wound onto reels up to 2400 feet.

The tape had seven parallel tracks, six for data and one to maintain parity (BCD character data were recorded in even parity whereas binary used odd parity). The recording density was 200 characters per inch, and initially the tape speed was 75 inches/second, so the transfer rate was 120 kbits/second. Later models increaded the transfer rate to 480 kbits/second.

A single 2400 foot tape could store about 3 MByte. Each tape would replace about 50,000 punched cards.

It would take about 250 tapes to fill one CD.

Images courtesy of Toronto Public Library.