IBM 729

<h2 id="data-format">Data format</h2>
<p>The tape had <a href="/facts/IBM_7-track/HSoVDxMh">seven parallel tracks</a>, six for data and one to maintain <a href="/facts/Parity_bit/peFp3Wau">parity</a>. 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. <a href="/facts/Write_protection/TkBtcIEG">Write protection</a> 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 <a href="/facts/Punched_card/44WsPulQ">punched cards</a> (about 4,000,000 six-bit bytes, a data quantity equivalent to three million octets).
</p><p>The 729 series was superseded by <a href="/facts/9-track_tape/5Eb6MjMr">9-track tape</a> drives introduced with the <a href="/facts/IBM_System%2f360/7znvpy4K">IBM System/360</a>.
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<h2 id="models">Models</h2>

<ul><li>729 I: The IBM 729 I was introduced for the <a href="/facts/IBM_709/N8RAWUTP">IBM 709</a> and <a href="/facts/IBM_705/8Gh15FSj">IBM 705 III</a> computers, looked identical to the <a href="/facts/IBM_727/1cHebYSp">IBM 727</a>, and used <a href="/facts/Vacuum_tube/VHd1BNLq">vacuum tubes</a>. The main improvement was the use of a dual gap head permitting write verify.</li>
<li>729 II: The IBM 729 II was introduced for the <a href="/facts/IBM_700%2f7000_series/8Gh15FSj">IBM 7000 series</a> computers, introducing a new cabinet style and <a href="/facts/Transistor/Bmr8zwL0">transistorized</a> circuitry. Supported dual density (200, 556).</li>
<li>729 III: High speed (112.5 in/s) single density (556).</li>
<li>729 IV: High speed (112.5 in/s) dual density (200, 556).</li>
<li>729 V: High density (800).</li>
<li>729 VI: High speed (112.6 in/s) high density (800). Introduced September 1961.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a></li></ul>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/IBM_7330/xt7t5AyC">IBM 7330</a>, a less expensive 7-track tape drive</li></ul>

<ul><li>IBM 709 Data Processing System, Form A22-6501-0</li></ul>
<h2 id="external-links">External links</h2>
<ul><li><a href="http://www.bitsavers.org/pdf/ibm/magtape/">Bitsavers.org Magnetic Tape Equipment manuals</a> (PDF files)</li>
<li><a href="https://www.youtube.com/watch?v=7Lh4CMz_Z6M">Debugging the 1959 IBM 729 Vacuum Column Tape Drive at the Computer History Museum</a>, YouTube 20 April 2016</li></ul>

Wikimedia Commons has media related to IBM 729.

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>DPD chronology <a href="https://web.archive.org/web/20100820215557/http://www-03.ibm.com/ibm/history/exhibits/dpd50/dpd50_chronology2.html" target="_blank">https://web.archive.org/web/20100820215557/http://www-03.ibm.com/ibm/history/exhibits/dpd50/dpd50_chronology2.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
</ol>

IBM 729 open-in-new

IBM 729