PDP-5

<h2 id="history">History</h2>
An earlier 12-bit computer, named <a href="/facts/LINC/ozNdFrHB">LINC</a> has been described as the first minicomputer<a class="footnote-ref" id="fnref:2" href="#fn:2">2</a> and also "the first modern personal computer."<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a> It had 2,048 12-bit words, and the first LINC was built in 1962.
DEC's founder, <a href="/facts/Ken_Olsen/0v0p1kYV">Ken Olsen</a>, had worked with both it and a still earlier computer, the <a href="/facts/18-bit/CgrYUIxM">18-bit</a> 64,000-word <a href="/facts/TX-0/8Bau5eqq">TX-0</a>, at <a href="/facts/MIT/Xk49vNA8">MIT</a>'s <a href="/facts/MIT_Lincoln_Laboratory/ea2JwxzT">Lincoln Laboratory</a>.
Neither of these machines was mass-produced.

<h2 id="applicability">Applicability</h2>
Although the LINC computer was intended primarily for laboratory use, the PDP-5's 12-bit system had a far wider range of use. An example of DEC's "The success of the PDP-5 ... proved that a market for minicomputers did exist"
is:

<ul><li>"Data-processing computers have accomplished for mathematicians what the wheel did for transportation"<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a></li>
<li>"Very reliable data was obtained with ..."<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a></li>
<li>"A PDP-5 computer was used very successfully aboard Evergreen<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a> for ..."<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a></li></ul>
all of which described the same PDP-5 used by the <a href="/facts/United_States_Coast_Guard/6d7SWTP9">United States Coast Guard</a>.
The architecture of the PDP-5 was specified by <a href="/facts/Alan_Kotok/uzbkQpAY">Alan Kotok</a> and <a href="/facts/Gordon_Bell/kEsh4EwF">Gordon Bell</a>; the principal logic designer was the young engineer <a href="/facts/Edson_de_Castro/WHf3JJ2I">Edson de Castro</a><a class="footnote-ref" id="fnref:8" href="#fn:8">8</a><a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> who went on later to found <a href="/facts/Data_General/EEABV3Gu">Data General</a>.

<h2 id="hardware">Hardware</h2>
By contrast with the 4-cabinet <a href="/facts/PDP-1/PSeIBDJU">PDP-1</a>,<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a> the minimum configuration of the PDP-5 was a single 19-inch cabinet with "150 printed circuit board modules holding over 900 transistors."<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a> Additional cabinets were required to house many peripheral devices.
The minimum configuration weighed about 540 pounds (240 kg).<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a>
The machine was offered with from 1,024 to 32,768 12-bit words of <a href="/facts/Core_memory/4TFIXSNd">core memory</a>. Addressing more than 4,096 words of memory required the addition of a Type 154 Memory Extension Control unit (in modern terms, a <a href="/facts/Memory_management_unit/tJQtAQzI">memory management unit</a>); this allowed adding additional Type 155 4,096 word core memory modules.<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a><a class="footnote-ref" id="fnref:14" href="#fn:14">14</a>

<h3>Instruction set</h3>
Of the 12 bits in each word, exactly 3 were used for instruction op-codes.<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a><a class="footnote-ref" id="fnref:16" href="#fn:16">16</a>
The PDP-5's instruction set was later expanded in its successor, the <a href="/facts/PDP-8/udvrynE8">PDP-8</a>. The biggest change was that, in the PDP-5, the program counter was stored in memory location zero, while on PDP-8 computers, it was a register inside the CPU. Another significant change was that microcoded instructions on the PDP-5 could not combine incrementing and clearing the accumulator, while these could be combined on the PDP-8. This allowed loading of many small constants in a single instruction on the PDP-8. The PDP-5 was one of the first computer series with more than 1,000 built.<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a><a class="footnote-ref" id="fnref:18" href="#fn:18">18</a>

<h2 id="software">Software</h2>
DEC provided <a href="/facts/Line_editor/DdVGP8uP">an editor</a>, an <a href="/facts/Assembler_(computing)/7XuV0cla">assembler</a>, a <a href="/facts/Fortran/m1KqjcMU">FORTRAN II</a> Compiler and
<a href="/facts/Dynamic_Debugging_Technique/jmRMJtmj">DDT</a> (a <a href="/facts/Debugger/mCe6UsWj">debugger</a>).<a class="footnote-ref" id="fnref:19" href="#fn:19">19</a>

<h2 id="marketplace">Marketplace</h2>
With a base price of $27,000 and designed for those not in need of the <a href="/facts/18-bit/CgrYUIxM">18-bit</a> <a href="/facts/PDP-4/oP3eBKVA">PDP-4</a>, yet having "applications needing solutions too complicated to be solved efficiently by modules systems" the PDP-5, when introduced in 1963, came at a time when the minicomputer market was gaining a foothold.<a class="footnote-ref" id="fnref:20" href="#fn:20">20</a><a class="footnote-ref" id="fnref:21" href="#fn:21">21</a>

<h2 id="photos">Photos</h2>
<ul><li><a href="http://collection.maynardhistory.org/items/show/5708">PDP-5 computer, including Teletype Model 33 ASR</a></li>
<li><a href="http://ed-thelen.org/comp-hist/vs-dec-pdp-5.jpg">PDP-5 from Ed Thelen's collection</a></li>
<li><a href="http://www.mcmanis.com/chuck/computers/images/pdp5-panel.jpg">Front panel of a PDP-5</a></li></ul>
<h2 id="notes">Notes</h2>

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

<ol>
<li id="fn:1">DIGITAL EQUIPMENT CORPORATION – Nineteen Fifty-Seven To The Present (PDF). Digital Equipment Corporation. 1975. <a href="http://s3data.computerhistory.org/pdp-1/dec.digital_1957_to_the_present_(1978).1957-1978.102630349.pdf" target="_blank">http://s3data.computerhistory.org/pdp-1/dec.digital_1957_to_the_present_(1978).1957-1978.102630349.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">"Wesley Clark Builds the LINC, Perhaps the First Mini-Computer". <a href="http://www.historyofscience.com/G2I/timeline/index.php?id=1006" target="_blank">http://www.historyofscience.com/G2I/timeline/index.php?id=1006</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">John Markoff, New York Times (March 4, 2016). "Wesley A. Clark, 88; MIT pioneer made computing personal". The Boston Globe (NY Times-owned). <a href="https://www.bostonglobe.com/metro/obituaries/2016/03/03/wesley-clark-dies-made-computing-personal/BapkdsEIMLnkOVcv3QrxGO/amp.html" target="_blank">https://www.bostonglobe.com/metro/obituaries/2016/03/03/wesley-clark-dies-made-computing-personal/BapkdsEIMLnkOVcv3QrxGO/amp.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">John P. Callahan (June 14, 1965). "COMPUTER AN AID IN OCEAN STUDIES; Statistical Tasks Are Eased During Ice Patrol Season 1964". The New York Times. <a href="https://query.nytimes.com/gst/abstract.html?res=9B00E2DB1F30E033A25757C1A9609C946491D6CF&legacy=true" target="_blank">https://query.nytimes.com/gst/abstract.html?res=9B00E2DB1F30E033A25757C1A9609C946491D6CF&legacy=true</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">"COAST GUARD WASHINGTON D C OCEANOGRAPHIC UNIT". WorldCat.org. <a href="http://www.worldcat.org/identities/nc-coast%20guard%20washington%20d%20c%20oceanographic%20unit" target="_blank">http://www.worldcat.org/identities/nc-coast%20guard%20washington%20d%20c%20oceanographic%20unit</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">U. S. Coast Guard Oceanographic Vessel — Evergreen (WAGO-295) <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">Herbert W. Graham (3 May 2022). "United States Report to ICNAF On Status of the Fisheries and Research Conducted in Calendar Year 1965" (PDF). p. 1a. <a href="https://www.nefsc.noaa.gov/publications/series/whlrd/whlrd6603.pdf" target="_blank">https://www.nefsc.noaa.gov/publications/series/whlrd/whlrd6603.pdf</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Best, Richard; Doane, Russell; McNamara, John (1978). "Digital Modules, The Basis for Computers". Computer Engineering, A DEC view of hardware systems design (PDF). Digital Press. Archived (PDF) from the original on 2010-03-12. <a href="http://research.microsoft.com/en-us/um/people/gbell/computer_engineering/00000125.htm" target="_blank">http://research.microsoft.com/en-us/um/people/gbell/computer_engineering/00000125.htm</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Reddy, Raj. "Nomination form for Edson de Castro to the National Academy of Engineering". Carnegie Mellon University Libraries Digital Collections. Carnegie Mellon University. Archived from the original on 2018-01-22. <a href="https://web.archive.org/web/20180122125458/http://digitalcollections.library.cmu.edu/awweb/awarchive?type=file&item=354096" target="_blank">https://web.archive.org/web/20180122125458/http://digitalcollections.library.cmu.edu/awweb/awarchive?type=file&item=354096</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Ed Thelen. "PDP-1". <a href="http://ed-thelen.org/comp-hist/pdp-1.html" target="_blank">http://ed-thelen.org/comp-hist/pdp-1.html</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">"The Rise and Fall of Minicomputers". 24 October 2019. <a href="http://ethw.org/Rise_and_Fall_of_Minicomputers" target="_blank">http://ethw.org/Rise_and_Fall_of_Minicomputers</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">PDP-5 Maintenance Manual (PDF). Digital Equipment Corporation. October 1964. p. 1-13. <a href="http://www.bitsavers.org/pdf/dec/pdp5/F-57_pdp5maint_Oct64.pdf" target="_blank">http://www.bitsavers.org/pdf/dec/pdp5/F-57_pdp5maint_Oct64.pdf</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Programmed Data Processor 5, Digital Equipment Corp., Mar. 1964; this is a promotional brochure. <a href="http://archive.computerhistory.org/resources/text/DEC/pdp-5/DEC.PDP-5.1964.102646094.pdf" target="_blank">http://archive.computerhistory.org/resources/text/DEC/pdp-5/DEC.PDP-5.1964.102646094.pdf</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
<li id="fn:14">"PDP-5 Price List" (PDF). Digital Equipment Corporation. October 1969. <a href="http://www.bitsavers.org/pdf/dec/pdp5/PDP-5_Price_List_Oct69.pdf" target="_blank">http://www.bitsavers.org/pdf/dec/pdp5/PDP-5_Price_List_Oct69.pdf</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></li>
<li id="fn:15">Programmed Data Processor 5, Digital Equipment Corp., Mar. 1964; this is a promotional brochure. <a href="http://archive.computerhistory.org/resources/text/DEC/pdp-5/DEC.PDP-5.1964.102646094.pdf" target="_blank">http://archive.computerhistory.org/resources/text/DEC/pdp-5/DEC.PDP-5.1964.102646094.pdf</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></li>
<li id="fn:16">Programmed Data Processor-5 Handbook (PDF). Digital Equipment Corporation. 1964. p. 12. <a href="http://www.bitsavers.org/pdf/dec/pdp5/F-55_PDP5Handbook_Feb64.pdf" target="_blank">http://www.bitsavers.org/pdf/dec/pdp5/F-55_PDP5Handbook_Feb64.pdf</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></li>
<li id="fn:17">"Programmed Data Processor-5". <a href="http://collection.maynardhistory.org/items/show/5708" target="_blank">http://collection.maynardhistory.org/items/show/5708</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></li>
<li id="fn:18">"PDP-5 Historical Interlude". 11 December 2014. <a href="https://videogamehistorian.wordpress.com/tag/pdp-5" target="_blank">https://videogamehistorian.wordpress.com/tag/pdp-5</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></li>
<li id="fn:19">Programmed Data Processor 5, Digital Equipment Corp., Mar. 1964; this is a promotional brochure. <a href="http://archive.computerhistory.org/resources/text/DEC/pdp-5/DEC.PDP-5.1964.102646094.pdf" target="_blank">http://archive.computerhistory.org/resources/text/DEC/pdp-5/DEC.PDP-5.1964.102646094.pdf</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></li>
<li id="fn:20">"Who Built the First Minicomputers Part II". <a href="http://tronola.com/html/who_built_the_first_minicomputers_part_ii.html" target="_blank">http://tronola.com/html/who_built_the_first_minicomputers_part_ii.html</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></li>
<li id="fn:21">DIGITAL EQUIPMENT CORPORATION – Nineteen Fifty-Seven To The Present (PDF). Digital Equipment Corporation. 1975. <a href="http://s3data.computerhistory.org/pdp-1/dec.digital_1957_to_the_present_(1978).1957-1978.102630349.pdf" target="_blank">http://s3data.computerhistory.org/pdp-1/dec.digital_1957_to_the_present_(1978).1957-1978.102630349.pdf</a> <a href="#fnref:21" class="footnote-back-ref">↩</a></li>
</ol>

PDP-5 open-in-new

PDP-5