PDP 11/34a

Last Updated: 02-May-2025

This is the oldest working computer in my collection and, in my opinion, the most impressive. This particular PDP came from a college, where it was sold by Tektronix to operate test equipment. The computer and drives have Tektronix serial numbers, and there is also a Tektronix HP-IB interface card used for connecting to the equipment.

My PDP has the following cards installed:

• M8266 - 11/34a control module
• M8265 - 11/34a data paths module
• M8267 - 11/34a floating point processor
• M7859 - Console interface
• M9312 - Bootstrap terminator
• M7856 - DL11-W Serial and realtime clock
• M9202 - Unibus jumper
• 2x M7891 - 128KB / 64Kword Memory
• M7762 - RL11 RL01/RL02 Drive controller
• Tektronix interface card
• M9302 - Terminator

Currently, I run the system with the RL11 controller removed and a Unibone in its place. The Unibone allows me to emulate drives, letting me experiment with more operating systems while also preserving the RL01s from wear.

Drives

This PDP came with two RL01 removable pack disk drives, each holding 5MB on a single platter. I only have two disk packs, and RL01 packs are much rarer than RL02s, which is a big reason why I opted for the Unibone. The first disk pack contained only XXDP+ diagnostics, while the second had an installation of Tektronix SPS BASIC, a custom dialect of BASIC developed by Tektronix based on Dartmouth BASIC. I uploaded an image of the disk here . You can easily boot this image in SIMH on an emulated 11/34A. Some manuals for Tek SPS BASIC can be found basic here.

Power supply repair

When I received the system, one of the H7441 5V regulators was broken. With help from some people on the VCFed forum, I was able to repair it. Read the thread here.