DEC PDP-11/23+

PDP 11/23 cabinet

This full PDP-11/23+ system was very kindly donated by Mudde AutoProc External link, a company who specialise in replacing old PDP, VAX and Alpha systems with new machines running emulation software. The system came with two RL02 drives and the following modules:

DEC M8192 KDJ11-AA LSI-11/73 CPU, 8-Kbyte cache
DEC M7195 MXV11-B 128-Kbyte RAM, 2 async EIA SLU, I/O, clock, 2 28-pin ROM sockets
DEC M8029 RXV21 RX02 floppy disk controller
DEC M8639 RQDX1 RD51/52 & RX50 MFM Disk control module
DEC M3104 DHV11-A 8-line Asynchronous Multiplexor, with DMA
DEC M7504 DEQNA-M Qbus to Ethernet adapter
DEC M7605 TQK25 TK25 0.25" streaming tape drive controller
NSC 980110014-211 National Semiconductor memory board (approx. 4MB)

Not all of these cards are installed as many are for devices I don't have connected. I later picked up the following extra modules:

DEC M8061 RLV12 RL01/RL02 disk controller (surprisingly missing from the original configuration)
DEC M7555 RQDX3 MFM disk controller ("upgrade" for the RQDX1)

Looking up the part numbers in this field guide External link, I initially wondered why what appeared to be the wrong CPU was installed. Turns out this machine had been upgraded with the 11/73's CPU as detailed in this DEC micronote External link.

The machine and its cabinet were in pretty good condition when they arrived. All that was really needed was a thorough clean-up, which meant taking pretty much the whole thing apart. It took a few evenings of work to get things looking as they're pictured here.

As can be expected, a few plastic parts had yellowed (most notably the "DEC Datasystem" bezel) but this isn't much of an issue: apart from the RL02 drives, which came up nicely with a little household cleaner and ample elbow grease, pretty much eveything is made of metal. This makes it a heavy old beast - I had to remove the two RL02s (each themselves weighing in at around 34kg) before having any chance of rolling the cabinet up a ramp to get over the front doorstep and doorframe!

Various bits of foam used to pad out cable clips and seal up parts of the system box had almost completely disintegrated and had to be replaced. The same was true of the coarse air filters in the front of the RL02s which had split in two. I was able to salvage the foam soundproofing on the inside of the cabinet's side panels, although it may be a good idea to remove and/or replace this as the foam tends to decay into a fine dust which can't be good for the computer itself.

More details are available on the folowing pages:

In the hope that it will be useful to other entusiasts, and also for my own reference, I've been documenting my progress with this machine. The initial primary goal to get Unix running on the PDP-11 has since been achieved (see the pages on installing 2.11BSD and Unix V7M below) but I'm also trying to maintain a to-do list of things that need to be sorted.