PDP-5

An earlier 12-bit computer, named LINC has been described as the first minicomputer{{cite web

|url=http://www.historyofscience.com/G2I/timeline/index.php?id=1006

|title=Wesley Clark Builds the LINC, Perhaps the First Mini-Computer}} and also "the first modern personal computer."{{cite news |newspaper=The Boston Globe (NY Times-owned)

|title=Wesley A. Clark, 88; MIT pioneer made computing personal

|url=https://www.bostonglobe.com/metro/obituaries/2016/03/03/wesley-clark-dies-made-computing-personal/BapkdsEIMLnkOVcv3QrxGO/amp.html

|author=John Markoff, New York Times |date=March 4, 2016}} It had 2,048 12-bit words, and the first LINC was built in 1962.

DEC's founder, Ken Olsen, had worked with both it and a still earlier computer, the 18-bit 64,000-word TX-0, at MIT's Lincoln Laboratory.

Neither of these machines was mass-produced.

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:

• "Data-processing computers have accomplished for mathematicians what the wheel did for transportation"{{cite news |newspaper=The New York Times

|url=https://query.nytimes.com/gst/abstract.html?res=9B00E2DB1F30E033A25757C1A9609C946491D6CF&legacy=true

|title=COMPUTER AN AID IN OCEAN STUDIES; Statistical Tasks Are Eased During Ice Patrol Season 1964

|date=June 14, 1965 |author=John P. Callahan}}

• "Very reliable data was obtained with ..."{{cite web

|url=http://www.worldcat.org/identities/nc-coast%20guard%20washington%20d%20c%20oceanographic%20unit

|title=COAST GUARD WASHINGTON D C OCEANOGRAPHIC UNIT |website=WorldCat.org}}

• "A PDP-5 computer was used very successfully aboard EvergreenU. S. Coast Guard Oceanographic Vessel — Evergreen (WAGO-295) for ..."{{cite web

|url=https://www.nefsc.noaa.gov/publications/series/whlrd/whlrd6603.pdf

|title=United States Report to ICNAF On Status of the Fisheries and Research Conducted in Calendar Year 1965|author=Herbert W. Graham| date=3 May 2022 |page=1a}}

all of which described the same PDP-5 used by the United States Coast Guard.

The architecture of the PDP-5 was specified by Alan Kotok and Gordon Bell; the principal logic designer was the young engineer Edson de Castro{{cite book|first1=Richard|last1=Best|first2=Russell|last2=Doane|first3=John|last3=McNamara|chapter-url=http://research.microsoft.com/en-us/um/people/gbell/computer_engineering/00000125.htm|chapter=Digital Modules, The Basis for Computers|url=http://bitsavers.org/pdf/dec/_Books/Bell-ComputerEngineering.pdf |archive-url=https://web.archive.org/web/20100312072729/http://www.bitsavers.org/pdf/dec/_Books/Bell-ComputerEngineering.pdf |archive-date=2010-03-12 |url-status=live|title=Computer Engineering, A DEC view of hardware systems design|publisher=Digital Press|date=1978}}{{cite web|last1=Reddy|first1=Raj|title=Nomination form for Edson de Castro to the National Academy of Engineering|url=http://digitalcollections.library.cmu.edu/awweb/awarchive?type=file&item=354096|website=Carnegie Mellon University Libraries Digital Collections|publisher=Carnegie Mellon University|archive-url=https://web.archive.org/web/20180122125458/http://digitalcollections.library.cmu.edu/awweb/awarchive?type=file&item=354096 |archive-date=2018-01-22 }} who went on later to found Data General.

By contrast with the 4-cabinet PDP-1,{{cite web|url=http://ed-thelen.org/comp-hist/pdp-1.html

|title=PDP-1|author=Ed Thelen}} the minimum configuration of the PDP-5 was a single 19-inch cabinet with "150 printed circuit board modules holding over 900 transistors."{{cite web

|url=http://ethw.org/Rise_and_Fall_of_Minicomputers |title=The Rise and Fall of Minicomputers| date=24 October 2019 }} Additional cabinets were required to house many peripheral devices.

The minimum configuration weighed about {{convert|540|lb|kg}}.{{cite book|url=http://www.bitsavers.org/pdf/dec/pdp5/F-57_pdp5maint_Oct64.pdf|title=PDP-5 Maintenance Manual|publisher=Digital Equipment Corporation|date=October 1964|page=1{{hyphen}}13}}

The machine was offered with from 1,024 to 32,768 12-bit words of core memory. Addressing more than 4,096 words of memory required the addition of a Type 154 Memory Extension Control unit (in modern terms, a memory management unit); this allowed adding additional Type 155 4,096 word core memory modules.[http://archive.computerhistory.org/resources/text/DEC/pdp-5/DEC.PDP-5.1964.102646094.pdf Programmed Data Processor 5], Digital Equipment Corp., Mar. 1964; this is a promotional brochure.{{cite web|url=http://www.bitsavers.org/pdf/dec/pdp5/PDP-5_Price_List_Oct69.pdf|title=PDP-5 Price List|publisher=Digital Equipment Corporation|date=October 1969}}

Of the 12 bits in each word, exactly 3 were used for instruction op-codes.{{cite book|url=http://www.bitsavers.org/pdf/dec/pdp5/F-55_PDP5Handbook_Feb64.pdf|title=Programmed Data Processor-5 Handbook|publisher=Digital Equipment Corporation|year=1964|page=12}}

The PDP-5's instruction set was later expanded in its successor, the PDP-8. 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.{{cite web

|url=http://collection.maynardhistory.org/items/show/5708

|title=Programmed Data Processor-5}}

DEC provided an editor, an assembler, a FORTRAN II Compiler and

DDT (a debugger).

With a base price of $27,000 and designed for those not in need of the 18-bit PDP-4, 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.{{cite web

|url=http://tronola.com/html/who_built_the_first_minicomputers_part_ii.html

|title=Who Built the First Minicomputers Part II}}

• [http://collection.maynardhistory.org/items/show/5708 PDP-5 computer, including Teletype Model 33 ASR]
• [http://ed-thelen.org/comp-hist/vs-dec-pdp-5.jpg PDP-5 from Ed Thelen's collection]
• [http://www.mcmanis.com/chuck/computers/images/pdp5-panel.jpg Front panel of a PDP-5]

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{{DEC hardware}}

Category:DEC minicomputers

Category:12-bit computers

Category:Transistorized computers

Category:Computer-related introductions in 1963