Digital Equipment Corporation PDP-11/73

Specifications

chunga

Aaah, my very own PDP-11! Although it's unfortunate that it isn't a model with a big front panel with lights and switches, it's still a very wonderful machine. Besides, it's probably a good thing that it isn't huge or sucks up power like it's going out of fashion.

To be technically accurate, this is actually a PDP-11/83 regardless of what it says on the cabinet. It must have been upgraded at some point as the PDP-11/73 uses the KDJ11-A CPU which is a dual width board and can only use Qbus memory. This unit has the KDJ11-B CPU which is a quad width board and can use the faster PMI (Private Memory Interconnect) memory.

I had received this with a single 1M Qbus RAM board and have recently upgraded it with a pair of 2M PMI RAM boards. This brings it up to its full 4M of RAM. Another addition is a Dilog SCSI controller and a 320M SCSI hard disk to replace the old dead 70M RD53 MFM hard disk. The RD53 used to work and, although I have another to replace it, they are notorious for premature death. Besides, SCSI drives are more common, have more storage, and are more relaible.

Another nice thing is that it's relatively small, compared to a refrigerator, and one of the more powerful models from the PDP-11 family. It offers power and features comparable to the PDP-11/70, which is quite a magnitude larger and consumes considerably more power, like the kernel/supervisor/user modes and split instruction/data spaces. One of the cool things about this machine is that it can run Unix quite nicely. This specimen has 2.11BSD on it which is the most modern Unix that can run on it.

Below is a list of the cards installed in it.