These pages are dedicated to the famous PDP-11 computer line, made by Digital Equiment Corporation (DEC) between 1970 and 1990.

Protect me from what I want

In spring 2008 I made an old and long forgotten dream come true and bought a PDP-11/44. I also downloaded all available documentation and began to understand the design of PDP-11 architecture and the way DEC built them. I also learned to handle the SimH vintage computer simulator, and wrote own educational and diagnostic software to get better handling and understanding on my very special 11/44.

My “PDP-11” project splits into several parts, and so does this web site:

  • Main part is the completion and restoration of my PDP-11/44.
  • First tests I made with XXDP on emulated TU58 tape. Here is a walkthrough for a 11/34.
  • Since the 11/44 is accesssible trough a quite archaic ASCII-console, I wrote a graphical development surface for PDP11’s and SimH: PDP11GUI
  • modified SimH 3.8 to interface to PDP11GUI. SimH needed telnet access to its console.
  • I modified the MACRO11 cross assembler for Win32.
  • Of course I was always fascinated by the ancient “light and switches” consoles of those early computers. As soon as I could get one, I bought the console panel of a PDP-11/70 and build an USB interface for it.
  • After my 11/44 run, I installed a 2.11BSD UNIX onto it.

The perfect hobby ...

... is of course a family with a dog! But restoring and running an PDP-11 is surely a less secret science. Many people are doing it, and many of them publish their experience on websites. A good entry into the PDP-11 world is the wikipedia article, then just follow the link lists. I will concentrate on topics very special to my own project.

Almost all documentation that DEC ever published is gathered on archive pages like or, Documentation includes schematics of the printed circuit boards, deep functional explanations of cpu microcode, guides how to set up operatings systems and other hard core stuff. Even better: DEC designed the PDP-11 for mass production, robustness, maintainability and comprehensibility for users. So it’s difficult to damage anything, defect components can be replaced easily, machines are easy to understand, and the ability to selftest is incorporated into many components. Complete diagnostic software (MAINDEC) is available as well. Most major operation systems and application software are available in various image formats. There are many sources for spare parts: commercial sites as well as a private eBay dealers (and don’t believe that everything is “Very rare!”). There are user groups as alt.sys.pdp11.

And you can simulate any system configuration with Bob Supniks “SimH simulator”. I use SimH heavily to compare my real PDP-11/44, which has some defects, with a sound simulation.

So no  excuse can be accepted: go and save one of those wonderful machines ... NOW!