PDP-8/S #1

Digital Equipment PDP-8/S, S/N 517

PDP-8/S rescue and restoration blog.

Software that came with the PDP-8/S.

The PDP-8/S was introduced in 1966 as a low cost version of the PDP-8. The "S" is said to stand for Small, but most say it stands for Slow. It was about 10% of the performance of the PDP-8 and about 20% of the cost. The $10,000 price included 4K of core memory that was expandable to 32K. The successor PDP-8 models that were introduced in the early 70s were much faster than the PDP-8/S and also supported DECtape magnetic tape drives. Most of the (1000 or 1500 depending on the source) PDP-8/S systems were scrapped. There is one at the Computer History Museum, one at the Living Computer Museum, one at the Goodwill Computer Museum, and just a few in private collector's hands.

This DEC PDP-8/S was donated to the RICM by a Robin Katz Banks. It was originally used to analyze heart regional and global wall motion data from a very high speed X-ray system at Temple University in Philadelphia, PA.

This system has 4K of core memory. There were no disks or tapes on this system, all information was read and saved on paper tape.

The PDP-8/S was introduced on 23-AUG-1966. It was designed by Saul P. Dinman and was the first CPU to cost less than $10,000. It is constructed entirely from standard DEC flip-chips and does not contain any integrated circuits. Just the processor contains 1001 transistors. The internal architecture of the CPU is serial making it much slower than other PDP-8 systems. The CPU instruction set is also a little different, so it will not run the same software as other PDP-8 systems.

Click on the image for a larger view.

The assembly at the top left is a PT08B teletype interface that has been modified for variable baud rate.

The Wire-Wrap assemble with the yellow wire is the PC0 controller that holds the Type 750/PC01 paper tape reader controller and the Type 75A paper tape punch controller.

The PC01 below the CPU cabinet is a combination of a PC02 paper tape reader and a PC03 paper tape punch. This reader/punch was also sold as a PC09 for the PDP-9.

This advertisement is from June, 1966. (Source: http://www.dvq.com)

Warren Stearns demonstrates how to read a test paper tape on a 45 year old Digital Equipment PDP-8/S computer. This is the first time that this has been attempted on this computer in possibly 30 years.

A top view of the inside of the CPU. The assembly near the bottom left of this image is the 4K words of core memory. Just to confuse people this core implementation is referred to as the 8K version even though it stores 4K.

The bottom of the CPU showing the Wire-Wrap connections between the Flip-Chips. In DEC tradition the blue wires are modifications or repairs.

The right side of the CPU, clearly showing the descrete components on the Flip-Chips.

A close up showing some the discrete components that make up the CPU.

The front of the CPU chassis.

This is what the processor looks like when it is running. The lights at the right show what type of instuction is being executed.

The rear of the