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IBM cassette tape
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<h2 id="use">Use</h2> <p>An IBM PC with just an external cassette recorder for storage can only use the built-in <a href="/facts/ROM_BASIC/aTec7AQY">ROM BASIC</a> as its <a href="/facts/Operating_system/8XTuvMh2">operating system</a>, which supports cassette operations. <a href="/facts/IBM_PC_DOS/ScsfqAwQ">IBM PC DOS</a> has no native support for cassette tapes, though software can be written to provide support. </p><p><a href="/facts/BIOS_interrupt_call/UThr5YWN">BIOS interrupt call</a> 15<a href="/facts/Hexadecimal/02ohQW22">h</a> routines are documented in the technical reference manual that turns the cassette motor on and off, and read or write data. Data is written with a lead-in section, and formatted in 256-<a href="/facts/Byte/BNHUp9Qq">byte</a> blocks with a 2-byte <a href="/facts/Cyclic_redundancy_check/u2exo4sv">CRC</a>.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> Programmers can also operate the cassette relay by writing to its <a href="/facts/I%2fO_address/PmLNFq01">I/O address</a>. The cassette, disk, advanced, and cartridge versions of <a href="/facts/IBM_BASIC/aTec7AQY">IBM BASIC</a> includes statements for cassette operations, but these features only work if the machine had a cassette port. </p><p>The data transfer speed is from 1-2 <a href="/facts/Kilobit/I79XYhdw">kilobits</a> per second, compared to the disk drive's 250 kilobits per second.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p><p>In 2020, the cassette interfaces of the IBM PC and PCjr were utilized to boot <a href="/facts/FreeDOS/61fuGd0j">FreeDOS</a> off a custom <a href="/facts/Vinyl_disc/ccuFV9Af">vinyl disc</a>.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a><a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p> <h2 id="data-format">Data format</h2> <p>The technical reference for the IBM PC 5150 specifies that the WRITE-BLOCK routine turns on the cassette drive motor and transforms each byte into <a href="/facts/Bit/S972NSaD">bits</a>. A (1) bit corresponds to a 1.0 <a href="/facts/Millisecond/xHCyv235">ms</a> timer period, (0) bit corresponds to 0.5 ms, which results in a recording speed of 1000 - 2000 <a href="/facts/Bit%2fs/ppUNMmVd">bit/s</a>. </p><p>First 256 bytes of 11111111 is written. One synchronization bit 0. A synchronization byte of 0x16. 256-byte blocks of data and a 2-byte <a href="/facts/Cyclic_redundancy_check/u2exo4sv">CRC</a> is written until all data is transferred.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h2 id="connector-pinout">Connector pinout</h2> <p>The IBM PC uses a female 5-pin <a href="/facts/DIN_connector/RwdLDTBC">DIN connector</a> (the same as the keyboard connector) for the cassette port: </p><p>Pinout:<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> </p> <ul><li>Pin 1: MOTOR CONTROL COMMON</li> <li>Pin 2: <a href="/facts/Ground_(electricity)/F6TEMIVv">GND</a></li> <li>Pin 3: MOTOR CONTROL (6 <a href="/facts/Volt/KF18MXP2">V</a>/1 <a href="/facts/Ampere/MScqkCgz">A</a>) RELAY</li> <li>Pin 4: DATA-IN (500 <a href="/facts/Nanoampere/rcKdfC2R">nA</a> with 13 V at 1000-2000 <a href="/facts/Baud/uCsmXrdT">Baud</a>)</li> <li>Pin 5: DATA-OUT (250 <a href="/facts/%25CE%259CA/rcKdfC2R">μA</a> <a href="/facts/Jumper_(computing)/dmQvs4ck">jumperable</a> either at 0.68 V ("<a href="/facts/Auxiliary_connector/KvpIlV94">AUX</a>") or 75 <a href="/facts/Millivolt/KF18MXP2">mV</a> ("<a href="/facts/Microphone_jack/KvpIlV94">MIC</a>"))</li></ul> <p>Motor control: <a href="/facts/Intel_8255/JAIeF77r">8255A</a> port 0x61, bit 3: 0 = on, 1 = off. </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Commodore_Datasette/AwtlrFyC">Commodore Datasette</a></li> <li><a href="/facts/IBM_Cassette_BASIC/aTec7AQY">IBM Cassette BASIC</a></li> <li><a href="/facts/Kansas_City_standard/aohbCQus">Kansas City standard</a></li> <li><a href="/facts/Tarbell_Cassette_Interface/Cpwp4YIs">Tarbell Cassette Interface</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Williams, Gregg (January 1982). "A Closer Look at the IBM Personal Computer". BYTE. p. 36. Retrieved 2013-10-19. <a href="https://archive.org/stream/byte-magazine-1982-01/1982_01_BYTE_07-01_The_IBM_Personal_Computer#page/n37/mode/2up" target="_blank">https://archive.org/stream/byte-magazine-1982-01/1982_01_BYTE_07-01_The_IBM_Personal_Computer#page/n37/mode/2up</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Libes, Sol (October 1982). "Bytelines". BYTE. p. 455-458. Retrieved 2024-12-30. <a href="https://archive.org/details/byte-magazine-1982-10/page/n452/mode/1up?view=theater" target="_blank">https://archive.org/details/byte-magazine-1982-10/page/n452/mode/1up?view=theater</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>"IBM PC Diagnostics 1.02 (Cassette)". WinWorld. <a href="https://winworldpc.com/product/ibm-pc-diagnostics/102-cassette" target="_blank">https://winworldpc.com/product/ibm-pc-diagnostics/102-cassette</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Norton, Peter (1985). The Peter Norton Programmer's Guide to the IBM PC. Microsoft Corporation. ISBN 0-91484546-2. I have never encountered a PC program on tape for sale. In fact, about the only use of the cassette port that I am aware of is the homespun and jerry-rigged use of this port as a poor-man's serial port. <a href="0-91484546-2" target="_blank">0-91484546-2</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>"Nerdly Pleasures: Tape Cassette Storage with the IBM PC and PCJR". 2014-04-20. <a href="http://nerdlypleasures.blogspot.com/2014/04/tape-cassettes-storage-with-ibm-pc-and.html" target="_blank">http://nerdlypleasures.blogspot.com/2014/04/tape-cassettes-storage-with-ibm-pc-and.html</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"IBM PC and PCjr Cassette Waveforms". 091207 <a href="http://www.brutman.com/Cassette_Waveforms/Cassette_Waveforms.html" target="_blank">http://www.brutman.com/Cassette_Waveforms/Cassette_Waveforms.html</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Williams, Gregg (January 1982). "A Closer Look at the IBM Personal Computer". BYTE. p. 36. Retrieved 2013-10-19. <a href="https://archive.org/stream/byte-magazine-1982-01/1982_01_BYTE_07-01_The_IBM_Personal_Computer#page/n37/mode/2up" target="_blank">https://archive.org/stream/byte-magazine-1982-01/1982_01_BYTE_07-01_The_IBM_Personal_Computer#page/n37/mode/2up</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Bogin, Jozef (2022-02-06) [2020-11-19]. "Booting from a vinyl record". Bogin, Jr. Archived from the original on 2023-08-06. Retrieved 2023-08-06. <a href="http://boginjr.com/it/sw/dev/vinyl-boot/" target="_blank">http://boginjr.com/it/sw/dev/vinyl-boot/</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Bogin, Jozef (2022-02-06). "IBM 4860 PCjr". Bogin, Jr. Archived from the original on 2023-06-03. Retrieved 2023-08-06. <a href="http://boginjr.com/electronics/old/ibm4860/" target="_blank">http://boginjr.com/electronics/old/ibm4860/</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>"IBM PC and PCjr Cassette Waveforms". 091207 <a href="http://www.brutman.com/Cassette_Waveforms/Cassette_Waveforms.html" target="_blank">http://www.brutman.com/Cassette_Waveforms/Cassette_Waveforms.html</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>IBM (1983). IBM PC Technical Reference Handbook. Comment: Also includes a complete listing of the ROM BIOS source code and schematics of the original IBM PC. <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> </ol>