Editing IBM 729

[[Image:IBM 729 Tape Drives.nasa.jpg|thumb|280px|A bank of IBM 729 tape drives]]
[[Image:Tapesticker.jpg|thumb|Reel of tape showing beginning-of-tape reflective marker]]
[[File:IBM 729 restored.jpg|thumb|An IBM 729 tape drive being debugged as part of the [[Computer History Museum]]'s [[IBM 1401]] restoration project. A reel of magnetic tape is being loaded onto the drive. The operator's finger is holding the tape in place on the take-up reel as he takes a few turns to secure the tape leader. An [[IBM 1403]] line printer is in the foreground.]]

The '''IBM 729 Magnetic Tape Unit''' was IBM's [[magnetic tape|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 [[IBM 700/7000 series|late 700, most 7000]] and many [[IBM 1400 series|1400]] series computers. Like its predecessor, the [[IBM 727]] and many successors, the 729 used {{convert|1/2|in|mm}} [[magnetic tape]] up to {{convert|2400|ft|m}} long wound on reels up to {{convert|10+1/2|in|mm}} diameter. To allow rapid tape acceleration (and thus reduced seek/access times), long [[Vacuum column (tape drive)|vacuum columns]] were placed between the tape reels and the [[tape head|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 [[IBM 7-track|seven parallel tracks]], six for data and one to maintain [[parity bit|parity]]. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity (709 manual, p.&nbsp;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&nbsp;inch gap between records allowed the mechanism enough time to stop the tape. Initial tape speed was 75&nbsp;inches per second (2.95&nbsp;m/s) and recording density was 200 characters per inch, giving a payload transfer speed of 90&nbsp;kbit/s (105&nbsp;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&nbsp;kbit/s; raw transfer rates up to 630&nbsp;kbit/s). At 200 characters per inch, a single 2400-foot tape could store the equivalent of some 50,000 [[punched card]]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]] drives introduced with the [[IBM System/360]].

== Models ==
[[file:Camp Smith, Hawaii. PFC Patricia Barbeau operates a tape-drive on the IBM 729 at Camp Smith. - NARA - 532417.jpg|thumb|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]] and [[IBM 705|IBM 705 III]] computers, looked identical to the [[IBM 727]], and used [[vacuum tube]]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 700/7000 series#IBM 7000 series, transistors, 1960s|IBM 7000 series]] computers, introducing a new cabinet style and [[transistor]]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.<ref>[https://web.archive.org/web/20100820215557/http://www-03.ibm.com/ibm/history/exhibits/dpd50/dpd50_chronology2.html DPD chronology]</ref>

==See also==
* [[IBM 7330]], a less expensive 7-track tape drive

== References ==
<references />
* IBM 709 Data Processing System, Form A22-6501-0

==External links==
* [http://www.bitsavers.org/pdf/ibm/magtape/ Bitsavers.org Magnetic Tape Equipment manuals] (PDF files)
* [https://www.youtube.com/watch?v=7Lh4CMz_Z6M Debugging the 1959 IBM 729 Vacuum Column Tape Drive at the Computer History Museum], YouTube 20 April 2016
<gallery>
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
File:Write protect ring.agr.jpg|Full-size, half-inch tape reel with [[Write protection|write enable]] rings
</gallery>

{{commons category|IBM 729}}
{{Magnetic tape data formats}}

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[[Category:IBM storage devices|729]]
[[Category:IBM 1400 series|729]]
[[Category:IBM 700/7000 series|Tape 729]]