PDP-5

PDP-5

PDP-5

12-bit computer from Digital

The PDP-5 was Digital Equipment Corporation's first 12-bit computer, introduced in 1963.[2]: p.5 

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History

An earlier 12-bit computer, named LINC has been described as the first minicomputer[3] and also "the first modern personal computer."[4] 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.

Applicability

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"[5]
  • "Very reliable data was obtained with ..."[6]
  • "A PDP-5 computer was used very successfully aboard Evergreen[NB 1] for ..."[7]

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[8][9] who went on later to found Data General.

Hardware

By contrast with the 4-cabinet PDP-1,[10] the minimum configuration of the PDP-5 was a single 19-inch cabinet with "150 printed circuit board modules holding over 900 transistors."[11] Additional cabinets were required to house many peripheral devices.

The minimum configuration weighed about 540 pounds (240 kg).[12]

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.[13][14]

Instruction set

Of the 12 bits in each word, exactly 3 were used for instruction op-codes.[13][15]

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.[16][1]

Software

DEC provided an editor, an assembler, a FORTRAN II Compiler and DDT (a debugger).[13]

Marketplace

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.[17][2]

Photos

Notes

  1. [N 1]
    U. S. Coast Guard Oceanographic Vessel — Evergreen (WAGO-295)

References

  1. [1]
    "PDP-5 Historical Interlude". 11 December 2014.
  2. [2]
    DIGITAL EQUIPMENT CORPORATION – Nineteen Fifty-Seven To The Present (PDF). Digital Equipment Corporation. 1975.
  3. [3]
    "Wesley Clark Builds the LINC, Perhaps the First Mini-Computer".
  4. [4]
    John Markoff, New York Times (March 4, 2016). "Wesley A. Clark, 88; MIT pioneer made computing personal". The Boston Globe (NY Times-owned).
  5. [5]
    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.
  6. [6]
    "COAST GUARD WASHINGTON D C OCEANOGRAPHIC UNIT". WorldCat.org.
  7. [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.
  8. [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.
  9. [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.
  10. [10]
    Ed Thelen. "PDP-1".
  11. [11]
    "The Rise and Fall of Minicomputers". 24 October 2019.
  12. [12]
    PDP-5 Maintenance Manual (PDF). Digital Equipment Corporation. October 1964. p. 1-13.
  13. [13]
    Programmed Data Processor 5, Digital Equipment Corp., Mar. 1964; this is a promotional brochure.
  14. [14]
    "PDP-5 Price List" (PDF). Digital Equipment Corporation. October 1969.
  15. [15]
    Programmed Data Processor-5 Handbook (PDF). Digital Equipment Corporation. 1964. p. 12.
  16. [16]
    "Programmed Data Processor-5".
  17. [17]
    "Who Built the First Minicomputers Part II".
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