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The IBM 729 Magnetic Tape Unit was IBM's tape mass storage system from the late 1950s through the mid-1960s. Part of the
IBM 7-track IBM's first magnetic-tape data storage devices, introduced in 1952, use what is now generally known as 7-track tape. The magnetic tape is wide, and there are six data tracks plus one parity track for a total of seven parallel tracks that span ...
family of tape units, it was used on late 700, most 7000 and many
1400 Year 1400 ( MCD) was a leap year starting on Thursday of the Julian calendar. The year 1400 was not a leap year in the Proleptic Gregorian calendar, it was a common year starting on Wednesday. Events January–March * January 4 ...
series computers. Like its predecessor, the IBM 727 and many successors, the 729 used
magnetic tape Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnetic ...
up to long wound on reels up to diameter. To allow rapid tape acceleration (and thus reduced seek/access times), long vacuum columns were placed between the tape reels and the read/write heads to absorb sudden increases in tape tension which would otherwise break the tape. Write protection was provided by a removable plastic ring in the back of the tape reel.


Data format

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 (709 manual, p. 20). Aluminum strips were glued several feet from the ends of the tape to serve as physical beginning and end of tape markers. Write protection was provided by a removable plastic ring in the back of the tape reel. A 3/4 inch gap between records allowed the mechanism enough time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch, giving a payload transfer speed of 90 kbit/s (105 kbit/s including parity bits). Later 729 models supported 556 and 800 characters/inch and 112.5 in/s (payload transfer rates up to 540 kbit/s; raw transfer rates up to 630 kbit/s). At 200 characters per inch, a single 2400-foot tape could store the equivalent of some 50,000
punched card A punched card (also punch card or punched-card) is a stiff paper-based medium used to store digital information via the presence or absence of holes in predefined positions. Developed over the 18th to 20th centuries, punched cards were widel ...
s (about 4,000,000 six-bit bytes, a data quantity equivalent to three million octets). The 729 series was superseded by
9-track tape 9-track tape is a format for magnetic-tape data storage, introduced with the IBM System/360 in 1964. The wide magnetic tape media and reels have the same size as the earlier IBM 7-track format it replaced, but the new format has eight data ...
drives introduced with the
IBM System/360 The IBM System/360 (S/360) is a family of mainframe computer systems announced by IBM on April 7, 1964, and delivered between 1965 and 1978. System/360 was the first family of computers designed to cover both commercial and scientific applicati ...
.


Models

PFC Patricia Barbeau operates an IBM 729 at Camp Smith, Hawaii, in 1969 * 729 I: The IBM 729 I was introduced for the
IBM 709 The IBM 709 is a computer system that was announced by IBM in January 1957 and first installed during August 1958. The 709 was an improved version of its predecessor, the IBM 704, and was the third of the IBM 700/7000 series of scientific compute ...
and IBM 705 III computers, looked identical to the IBM 727, and used
vacuum tube A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
s. The main improvement was the use of a dual gap head permitting write verify. * 729 II: The IBM 729 II was introduced for the IBM 7000 series computers, introducing a new cabinet style and
transistor A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...
ized circuitry. Supported dual density (200, 556). * 729 III: High speed (112.5 in/s) single density (556). * 729 IV: High speed (112.5 in/s) dual density (200, 556). * 729 V: High density (800). * 729 VI: High speed (112.6 in/s) high density (800). Introduced September 1961.DPD chronology
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See also

* IBM 7330, a less expensive 7-track tape drive


References

* IBM 709 Data Processing System, Form A22-6501-0


External links


Bitsavers.org Magnetic Tape Equipment manuals
(PDF files)
Debugging the 1959 IBM 729 Vacuum Column Tape Drive at the Computer History Museum
YouTube 20 April 2016 Image:Ibm-729v.jpg, An IBM 729 V at Deutsches Museum, Munich File:IBM 729 tape drives.agr.jpg.jpg, IBM 729 tape drives at Computer History Museum (CHM) File:IBM 729 side exposed.agr.jpg.jpg , Side view of 729 tape drive with cover removed at CHM File:IBM 729 cable.agr.jpg, Cable used to connect IBM 729 tape drives to each other and to an
IBM 1401 The IBM 1401 is a variable word length computer, variable-wordlength decimal computer that was announced by IBM on October 5, 1959. The first member of the highly successful IBM 1400 series, it was aimed at replacing unit record equipment for pr ...
computer at CHM File:Write protect ring.agr.jpg, Full-size, half-inch tape reel with write enable rings
{{DEFAULTSORT:Ibm 729 729 729 Tape 729