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The
IBM 727 Magnetic Tape Unit was announced for the
IBM 701The IBM 701, known as the Defense Calculator while in development, was announced to the public on April 29, 1952, and was IBM’s first commercial scientific computer...
and
IBM 702The IBM 702 was IBM's response to the UNIVAC—the first mainframe computer using magnetic tapes. Because these machines had less computational power than the IBM 701 and ERA 1103, which were favored for scientific computing, the 702 was aimed at business computing.The system used electrostatic...
on September 25, 1953. It became IBM's standard tape drive for their early
vacuum tubeIn electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
era computer systems. Later vacuum tube machines and first-generation transistor computers used the
IBM 729The IBM 729 Magnetic Tape Unit was IBM's iconic tape mass storage system from the late 1950s through the mid 1960s. Part of the IBM 7 track family of tape units, it was used on late 700, most 7000 and many 1400 series computers...
-series tape drive. The 727 was withdrawn on May 12, 1971.
The tape had
seven parallel tracksIBM's first magnetic tape data storage devices, introduced in 1952, use what is now generally known as 7 track tape. The magnetic tape is 1/2" wide and there are 6 data tracks plus 1 parity track for a total of 7 parallel tracks that span the length of the tape...
, six for data and one to maintain
parityA parity bit is a bit that is added to ensure that the number of bits with the value one in a set of bits is even or odd. Parity bits are used as the simplest form of error detecting code....
. 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 protectionWrite protection is any physical mechanism that prevents modification or erasure of valuable data on a device. Most commercial software, audio and video is sold pre-protected.-Examples:...
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 |
PET film BoPET is a polyester film made from stretched polyethylene terephthalate and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aroma barrier properties and electrical insulation.A variety of companies manufacture boPET and other...
(Mylar) or cellulose acetate base |
Sources