I have refurbished/built several small PDP-11/23's and sold or traded them, mostly on eBay. One purpose of this page is to serve as a useful reference for the people who now own these machines. Also, if you are interested in building your own PDP-11, this page might get you started.
Generally, each of these PDP-11/23's contains the following:
This hardware will run 2.9BSD UNIX.
You can easily and cheaply build one of these from parts which are readily available. Here is a picture of a minimal and very inexpensive PDP-11 that will run 2.9BSD UNIX.
The hard drive is a Seagate ST151 (40 megs). Other hard drives that work are ST251, ST4096, and Maxtor XT1140. Other necessary items that are not shown in the picture are: power supply with +5 and +12, cooling fans, a terminal such as a VT420, and the terminal cable. VTserver can be used to load UNIX from a PC, once the hard drive has been set up and formatted.
This PDP-11 must be cooled with forced air. If the fans stop, the CPU and hard drive controller will overheat and fail. Two small fans blowing through the cage from the side works.
Certain hard drives, among them the DEC RD54/Maxtor XT2190, and the XT1140, also must be cooled with forced air. They overheat and start to get data errors in still air.
The card cage is an H9281-BA.
The small card on the back supplies power-on reset and other signals needed to make the CPU run. This is in lieu of a console with reset and run/halt switches. This card does not supply LTC, which is needed for UNIX and some versions of RT-11 Kermit. I'm not sure what the card is called or who made it. The card is described here.
Last modified: December 31, 2009