website/content/museum/digital-equipment-corporation-pdp-8.md

---
title: Digital Equipment Corporation PDP-8
categories:
- Computers
types:
- Professional Computer
origins:
- U.S.A.
years:
- '1965'
params:
  name: PDP-8
  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
  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
  comments:
  - author: Oleg Kuznetsov (Russia)
    date: Thursday 28th November 2019
    text: Hi folks! I''m from Russia which in past was USSR - we worked on PDP 11/70 series machine in Moscow State University at the Department of Math and Mechanics in 1985-1990. These were indeed great times for us students to program on PDP using mostly Macro Assembler and C++ when it later was also enabled on this multi-user machine. We experimented with FORTRAN to calculate differential equations and find better applications for serious tasks in computing the big data. We also had quite a lot of TETRIS, SNAKE games on our hard disk and we used $UIC$ user entry system which allowed user to RUN and DEBUG the programs - there had been BUILDER of EXE files and this was not too easy to cope. While RSX operating system was quite a fun. All commands we used were well documented and helpful. We even tried to a bit hack the RSX shell to enter as highest priority user while this was only to "improve" our skills in the RSX system engine, And this system was and still IS state of the art I would
      suggest. I had SO many nice experience in general understanding of how OS works, what it''s core is and how system of machine commands works as one Orchestra. These WERE the times folks!!!! Br Oleg from Moscow
  - author: Chuck Rose (Vermont, USA)
    date: Friday 26th December 2014
    text: The first two of the first three machines I ever worked on were PDP-8''s. A PDP-8A in my high school freshman year in a computer math class and a PDP-8E in my junior and senior years in a computer science/data processing vocational program. They were incredible machines for their time. The one in the vocational program had 2 removable rk05e''s and an rk05f hard drives attached and had 15 terminals attached that could all be used at the same time! It did this with only 32k word memory (appx 48k bytes)! It used an operating system called ''ETOS'' which used the rk05f (5MB fixed version) for virtual memory, one of the rk05e''s for the OS and languages (BASIC, DIBOL, COBOL, and Fortran IV) and the other rk05e for data files.
  - author: Douglas W. Jones (Iowa City, Iowa, USA)
    date: Tuesday 18th February 2014
    text: |-
      I am currently leading a group of students in an attempt to restore PDP-8 serial number 85 to operating condition. Our restoration project log is on the web at:\
      $ http://www.cs.uiowa.edu/\~jones/pdp8/UI-8/\
      We''re posting photos of our work $ currently the focus is on reforming the capacitors in the power supply so we can turn it on. That will take a while, since we had to disassemble quite a bit just to get to some of them.
  - author: Bob (USA)
    date: Tuesday 12th February 2013
    text: |-
      I had the privilege of debugging PDP 8S serial no. 2 in the factory at Maynard in the Traditional products dept. in 1970. It had come to the factory to be rebuilt after being struck by lightning in some place in the Midwest.\
      It took me almost two months to repair and get it working again. I almost couldn''t believe It was working again after finding so many blown out transistors and other burnt components.
  - author: Bob (USA)
    date: Tuesday 12th February 2013
    text: |-
      I had the privilege of debugging PDP 8S serial no. 2 in the factory at Maynard in the Traditional products dept. in 1970. It had come to the factory to be rebuilt after being struck by lightning in some place in the Midwest.\
      It took me almost two months to repair and get it working again. I almost couldn''t believe It was working again after finding so many blown out transistors and other burnt components.
  - author: Chuck Rose (Vermont, USA)
    date: Saturday 24th September 2011
    text: Alex, perhaps you should also get your own facts straight. Unix was first written for the Digital PDP 7.... Not the 8 nor the 11. A quick look at any of the many Unix histories available online will confirm this.
  - author: alex
    date: Tuesday 12th April 2011
    text: Unix? Get your facts straight. It first ran on PDP-11.
  - author: CitizenPete (Ohio)
    date: Friday 1st October 2010
    text: |-
      @ A$exeo : Unix? Unix? Unix? are you kidding me?

      Ken Olsen would never allow any stinking penguin near any of his machines.

      RMS 4ever!

      LMAO
  - author: Chris (Home PC)
    date: Sunday 14th October 2007
    text: |-
      I have a friend who's dad OWNS two PDP-8s (plus three PDP-11s).

      I'm actually going to be getting one of the 8s and one of the 11s from her.

      Long live the PDP!
  - author: A;exeo (Seattle (USA))
    date: Wednesday 3rd May 2006
    text: Well, here it is. First to run UNIX! 12-bit for life. :D
  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.