---
title: Digital Equipment Corporation PDP-8
categories:
- Computers
types:
- Professional Computer
origins:
- U.S.A.
years:
- '1965'
params:
  name: PDP-8
  image: /media/museum/photos/dec_pdp8_system_1.jpg
  company: /companies/digital-equipment-corporation
  company_name: Digital Equipment Corporation
  specs:
  - label: NAME
    value: PDP-8
  - label: MANUFACTURER
    value: Digital Equipment Corporation
  - label: TYPE
    value: Professional Computer
  - label: ORIGIN
    value: U.S.A.
  - label: YEAR
    value: '1965'
  - label: END OF PRODUCTION
    value: '1980'
  - label: BUILT IN LANGUAGE
    value: None
  - label: KEYBOARD
    value: ASR-33 Teletype
  - label: CPU
    value: CPU was composed of 12 interlinked Register Boards
  - label: SPEED
    value: 1 MHz (0.5 MIPS)
  - label: RAM
    value: 4 K of 12 bit words
  - label: TEXT MODES
    value: Depending of the terminal used
  - label: SIZE / WEIGHT
    value: 48 (W) x 55 (D) x 84 (H) cm. / 150 Kgs.
  - label: I/O PORTS
    value: 110 Baud serial interface
  - label: BUILT IN MEDIA
    value: None
  - label: POWER SUPPLY
    value: Built-in 780 Watts power supply unit
  - label: PERIPHERALS
    value: Memory boards up to 32 Kwords
  - label: PRICE
    value: $18.000 (Basic version)
  tabs:
  - emulators
  - links
  forum_thread: 761
  emulators:
  - title: SIMH
    url: http://simh.trailing-edge.com/
    platform: Windows
    text: Windows emulator for a lot of mini computers. Sources are available so you can compile them for your own platform.
  - title: PDP-8/E
    url: http://www.bernhard-baehr.de/pdp8e/pdp8e.html
    platform: Apple
    text: emulator for the DEC PDP-8/E minicomputer running on the Apple Macintosh
  links:
  - title: Douglas W.Jones's DEC PDP8 Home Page
    url: http://www.cs.uiowa.edu/~jones/pdp8/
    text: Wow, tons of doc and info here !
  - title: More information about DEC PDP8 operating systems
    url: http://www.faqs.org/faqs/dec-faq/pdp8/section-10.html
    text: With PDP8 FAQ as well
  - title: PDP-8 Technology Before The Millennium
    url: http://www.pdp8.com/
    text: PDP-8 Restoration Notes
  - title: Yet Another PDP-8 Web Site
    url: http://www.pdp8.net/
    text: Lot of information and pictures
  related:
  - /museum/digital-equipment-corporation-vt78
  oc_id: 780
  source:
    url: https://web.archive.org/web/20230608091007/http://www.old-computers.com/museum/computer.asp?c=780
    date: '2023-06-08'
---

The PDP-8 was the first sucessful commercial minicomputer, produced by DEC in the 60s, the first real minicomputer, and the first computer costing less than $20,000.

By late 1973 to 77, the PDP-8 family was the best selling computer in the world. The basic version could sit on a desktop rather than requiring cumbersome racks well known at the time. This compact size caused it to become a popular system in scientific laboratories.

The machine had a now quite strange 12-bit word and four thousand 12-bit words of magnetic core memory. The first model was built without any Integrated circuit - thus no microprocessor - but with discrete transistors mounted on numerous small printed circuit boards called 'flip chips' that were inserted on two backplanes mounted vertically. Both table-top and rack-mount models were available, but adding additional memory required a rack.

CPU was composed of 12 interlinked Register Boards each operating on one bit slice of the 12 bit word and containing an Adder function together with all the major registers - MB, MA, AC, PC. Speed a little less than 1MHz.

The instructions set of the PDP-8 was very limited, only eight basic instructions encoded by the three left bits of each 12-bit word, and one register, the accumulator: However, the PDP-8 could be programmed to do almost anything. It just took longer (sometimes very longer!) to execute programs.

A 110 baud current loop teletype interface allowed an ASR 33 Teletype to be connected, serving as a console as well as a storage device by means of the built-in papertape puncher and reader.

There were numerous variations of the original model over the years, among them:\
1966: **PDP-8/S** - minimum price but slow memory serial logic design\
1968: **PDP-8/I** - first version with integrated circuits\
1970: **PDP-8/E** - New bus structure design called Omnibus\
1975: **PDP-8/A** - Allowed OEMs choice of memory type and quantity

All together, about 50,000 PDP-8 series computers were sold, as well as numerous clones made USA, Asia and East European countries.\
In 2000 year, there were still a few PDP8's in operation, mainly in third-world countries.