The 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 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 1/2" wide, and there are six data tracks plus one parity track for a total of seven parallel tracks th ...

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 (link will display the full calendar) of the Julian calendar. The year 1400 was not a leap year in the Proleptic Gregorian calendar. Events January–December * Henry IV of Englan ...

series computers. Like its predecessor, the IBM 727 and many successors, the 729 used 1/2 inch (12.7 mm)

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 magnet ...

up to 2400 feet (730 m) long wound on reels up to 10½ inch (267 mm) 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 Parity may refer to: * Parity (computing) ** Parity bit in computing, sets the parity of data for the purpose of error detection ** Parity flag in computing, indicates if the number of set bits is odd or even in the binary representation of the ...

. 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 cards (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 (nine) is the natural number following and preceding . Evolution of the Arabic digit In the beginning, various Indians wrote a digit 9 similar in shape to the modern closing question mark without the bottom dot. The Kshatrapa, Andhra and ...

drives introduced with the

IBM System/360 The IBM System/360 (S/360) is a family of mainframe computer systems that was announced by IBM on April 7, 1964, and delivered between 1965 and 1978. It was the first family of computers designed to cover both commercial and scientific applic ...

Models

729 I

The IBM 729 I was introduced for the

IBM 709 The IBM 709 was a computer system, initially 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 co ...

and IBM 705 III computers, looked identical to the IBM 727, and used

vacuum tube A vacuum tube, electron tube, 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 potential difference has been applied. The type known as ...

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 The IBM 700/7000 series is a series of large-scale (mainframe) computer systems that were made by IBM through the 1950s and early 1960s. The series includes several different, incompatible processor architectures. The 700s use vacuum-tube log ...

computers, introducing a new cabinet style and

transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...

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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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 computer at CHM {{DEFAULTSORT:Ibm 729 729 729 Tape 729