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DEC PDP-8/S #4

PDP-8/S (S/N 149) was donated by David Getty of Bedford Massachusetts. David provided the following information about the computer.
 

I acquired the computer (PDP-8/S) in 1970 when I was an Assistant Professor of Psychology at Brown University.  I and my students used the computer in perceptual studies, mostly in the study of human timing processes, important in speech and music production and perception.  The computer system was last fired up in 1976 when I left Brown to take up a position as a Senior Scientist at BBN Technologies in Cambridge.  The computer came with me to BBN, but I never set up the system again since BBN had much more advanced computing technologies available to me.  So, the computer system has been sitting in my garage unused since 1976. Yes, the wiring on the upper rack was designed and wrapped by me and my students, including I believe the controller for the Decitek reader and the high speed punch.  Other circuitry was indeed related to controlling experiments.  It interfaced with a Mac Panel device, which allowed us a great deal of flexibility in configuring experiments without rewiring the controller.

 As you’ll see in the photos, the computer is mounted in an open relay rack together with a Decitek high-speed paper tape reader and an expansion box containing a lot of wired logic modules (presumably circuitry for the tape reader, a high-speed paper tape punch—no longer with me, and I/O for controlling our experiments).  

Finally, I have a number of software programs I and my students developed, including especially PEPL (Psychology Experiment Programming Language).  Attached is a published paper describing PEPL.

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This is the Decitek Model 443A9 paper tape reader that was use with the system.
Decitek is still in business and sent us a replacement drive belt for this reader.
The belt has been replaced, but we need to adjust the position of the tape sprockets.

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Since there was no disk or magnetic tape drive on this system all of the software was loaded from paper tapes.

PDP-8S_ISZ-Increment-AC.MOV

On 10/27/12 the system was run for the first time in about 35 years.
This video shows an ISZ loop that increments the accumulator.

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A DEC H728 power supply is mounted in the bottom of the rack.
This supplies +10VDC@7A and -15VDC@8A.

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The Psychology Experiment electronics is at the top and middle.
The Decitek paper tape reader interface is at the bottom right.
The top rack is a DEC H900 Mounting Panel that accommodates 32 modules and includes a +10VDC and -15VDC.
The middle rack is a DEC 1943 that accommodates 64 modules.
The bottom rack is a DEC H911 that accommodates 64 36-pin modules.

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The Psychology Experiment electronics is at the top and middle.
The Decitek paper tape reader interface is at the bottom left.

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The PDP-8/S Processor chassis.
With only three module replacements it is mostly working.
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