The University of Iowa's DEC PDP-8

Part of the PDP-8 Collection
by Douglas W. Jones
THE UNIVERSITY OF IOWA Department of Computer Science

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The system. Front Panel.


Photo credit: Unless otherwise indicated, Douglas W. Jones. The right photo above was taken by Randy Dietrich.


This Digital Equipment Corporation PDP-8, serial number 85, was purchased to support Stephen S. Fox, who came to the University of Iowa in the fall of 1965. A 1966 report on computing at Iowa describes the machine:

5. Psychology

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Psychology Installation:
A PDP-8 System.
A PDP-8 computer was installed in the Psychology Department in the fall of 1965. The operation of this computer is under the direction of Dr. Stephen Fox, Associate Professor.

The configuration of the system has a processing unit with 4096 words (12-bit) of memory with a 1.6 microsecond cycle. The system has 12 channels of multiplexed analog to digital input. Two teletype stations with paper tape input/output are attached. The cost of this system was about $30,000.

Dr. Fox is using the PDP-8 computer for on line research studies in the field of behavioral neurophysiology. Experimental data is taken by the system from subjects through the teletype station and.or A-D sensors. Reduction and analysis of the data is also being done on the PDP-8 computer.

Current and planned research projects are limited by the configuration due to the lack of a high-speed medium of input/output. A means of attaching magnetic tape to the system is now being investigated.

When the System/360 Model 67 is installed at the University Computer Center, ...

Horton, Dick; et. al. A Report to the President: Computing at the University of Iowa: Study and Recommendations. 1966. 116 pages. University of Iowa Archives, cataloged section, call no. FOLIO QA76.9.C55 I57 1966

Judging by the evidence in the machine as we received it, the anticipated magnetic tape interface was eventually added, but the plan to interface it directly to a machine in the computer center was never carried out. Furthermore, the IBM 360-67 anticipated by this report was never delivered to the University of Iowa.

Here are quotations from some published research articles describing work done using this machine:

A simple on-line, real-time program for a PDP-8 laboratory computer system provided analog-to-digital conversion of the spontaneous electroencephalogram (EEG) each millisecond from a glass micropipette in the cortex of acutely prepared, curarized and locally anesthetized cats.

Functional Congruence: An Index of Neural Homogeneity and a New Measure of Brain Activity, Stephen S. Fox, Robert J. Norman, Science New Series, 159, 3820 (Mar. 15, 1968), 1257-1259.

The amplifier signal went to A-D channels of the PDP-8 ... The tone, triggered by the PDP-8, was a 20-msec train of 0.1-msec square pulses.

Operant Control of Neural Events in Humans, Joel P. Rosenfeld, Alan P. Rudell, Stephen S. Fox, Science New Series, 165, 3895 (Aug. 22, 1969), 821-823.

In 1966, the psychology department hired a computer science grad student, Max A. Dietrich, as a programmer, and he would later describe this machine as his personal computer. Another CS student also worked on this machine before Dietrich, Jeanne Schultz (possibly misspelled). Max Dietrich is credited for the software used in the first Science article cited above. After receiving his MS in 1968, he went to work for Digital and later Tandem Computers, where he spent the bulk of his career. *

By the early 1990s, the machine had been idle since the late 1970s, and it had been pushed into condemned space in an attic of Seashore Hall along with piles of other old apparatus.

When the psych department was told to prepare to vacate that space in the fall of 1992, they began sending equipment to surplus, but one of the technicians called the Computer Science department asking if it was interested in a genuine antique. As a result, on September 15, 1992, the machine was moved from Seashore Hall to MacLean hall, where a group of students briefly investigated the possibility of restoring the machine.

Unfortunately, the CS department needed that lab space, so the machine was pushed into a storeroom until 2013, when building remodelling forced that storeroom to be vacated. The machine was then pushed out into the hallway where it was tagged for University Surplus to remove. At about the same time, the CS department realized that restoring this PDP-8 would be an excellent way to celebrate the department's 50th anniversary (the department was founded in early 1965), so the machine was reclaimed from surplus, and on October 24, 2013, it was moved into space in the Communications Center formerly occupied by the Journalism department.

First-time visitors can take a tour of the system. For more detail on our progress restoring the system, see the chronological repair log and the enumeration of problems encountered.