System Number 319

The PDP-9 was a follow on to the highly successful DEC PDP-7 series of computers. While there were some differences, one of the PDP-9 system utilities would convert PDP-7 programs to run on the PDP-9. Input was by paper or magnetic tape.

This system was purchased by Max Levy Autograph in October 1968 and shipped to Concord Controls who designed and built the controller for the 60" photo-plotter. This was one of the largest such devices in the world. It was used to prepare glass for etching as filters and measuring templates. The photo-plotter rested on a five foot thick granite slab, with supports set in bedrock. The PDP-9 and photo-plotter was then shipped to  Philadelphia, PA and ran 24/7 from 1968 to the summer of 1999. When the memory limitations of the PDP-9 caused problems with programming they bought a PDP-11/23 and connected it to the PDP-9 through a special I/O controller that let the PDP-11/23 control the PDP-9.

We were contacted by Ted Heimberger, the person who operated this system for 30 years. He filled us in on much of the history of the system and will come to the RICM for a visit. The notes that are taped to the front of the system are his.

This PDP-9 was located for the RICM by Kevin Stumpf, and donated by Max Levy Autograph of Philadelphia, PA. A total of 445 PDP-9 systems were produced, and so far, only nine are known to have survived.

The current locations of these nine include a PDP-9 and a PDP-9/L in California, one in Australia that came from La Trobe University in Melbourne, one in Germany, one in Great Britain, two in France, two in Sweden and a new one #203, and of course our own, seen below. Parts of #209 that was delivered to Australia Iron & Steel were recently found. There are lots of details on the developers of the PDP-9 here.

Apparently the design of the ROP Control Memory in PDP-9 systems caused lots of problems. Lichen Wang from SLAC developed an improved design that proved more reliable. The description is here.

8,192 words of core memory with an 18-bit word length

1.0 usec cycle time

Real-Time Clock

Operator's Console

300 cps Paper Tape Reader

50 cps Paper Tape Punch

10 cps Console Teleprinter, Model KSR-33

The processor cost $35,000 in 1968.

The TC59 tape controller cost $10,000.

The TU20 tape drive cost $12,000.

The cost in 2020 dollars of this system would be $400,886.

With the TC02 DECtape controller and TU55s drives that we added the total is $502,513.

The PDP-9 Console.

The PC09 Paper Tape Reader/Punch and a TU55 DECtape drive are located above the control panel.

The PC0, S/N 863, contains a PC02 Paper Tape Reader and a PC03 Paper Tape Punch.

The cabinet to the right contains 2X TU55 DECtape drives, the TC02 DECtape controller, and the TC59 Magnetic Tape controler.

The magnetic tape drive to the left is a TU20 7-track drive. 

If the system was run 8 hours per day, this shows 20 years of run time.

The Core Memory Controller serial number matches the maintenance contract.

The Processor serial number tag is missing.

 The I/O controller serial number also matches the maintenance contract.

The PDP-9 system console.

The original configuration of the PDP-9 according to DEC.

There is a date of January 17, 1968 on many of the CPU fans. That is about right for the manufacturing date of this system.

The official production run was 445 PDP-9 systems. Additional systems were built on special order after production ended.

The PC0 paper tape reader/punch is S/N 863.

Rear view of the PDP-9 Processor.

Yellow wires are factory installed. Blue ones are design changes, probably made in the field. The green wires could be design changes or additions.