Lock Free


These pages exist for the purpose of sharing what I have learned about rebuilding Qbus PDP-11 computers. A PDP-11 can be restored or put together with a minimum amount of work from parts that are easily obtainable at a reasonable price. These machines can  run Ancient UNIX, RT-11, or other classic DEC operating systems. Qbus machines are small enough to run off a standard outlet (150 watts) and fit under a desk.

The hardware page describes the systems and some of the important boards.

I first built a PDP-11/23 running RT-11 and/or 2.9BSD UNIX. The 11/23 page shows how to build a minimal PDP-11 with four boards.

I have built several PDP-11/53's. The KDJ11 page now includes the critical and hard-to-find information needed to get an 11/53 CPU to talk to a console, and how to install the boot ROMs. The KDJ11-SD CPU board from a DECserver 500 or 550 is actually an 11/53 with different jumpers and ROMs. These show up fairly often on eBay and can be obtained for as little as $20~$25. I bought one for $5 once. The KDJ11 page show how to convert the KDJ11-SD into an 11/53 CPU.

I recently assembled a PDP-11/83 dream machine.

The software page describes the OSes and tools I'm using, and might be helpful to someone who is trying to bootstrap onto a PDP-11.

Here is where to get PDP-11's and parts.

[A few of the pages in this section were originally created with UNIX-ish file names (mixed case, multiple periods). The more recent version of Microsoft's Front Page I am using now enforces more restrictive file naming rules -- all lower case, periods are turned to underscore. This would break links to my web pages from other people's sites and search engines. Thank you, Microsoft. :-\  I therefore created by hand several small pages using the old names that redirect to the new names, for example: KDJ11.htm redirects to kdj11.htm.]


Last modified: December 31, 2009