Avram's Past

My first computer (the PDP-7 1966)


In 1966 when I was 21, I had a major career decision to make.  My main choices were between being a poet (I actually wrote some pretty good poems),  being a musician (but all buddies wanted to get stone and then practice while I wanted to practice and then get stoned),  go to jail a lot protesting the war (Vietnam then), becoming a Hassidic Rabbi or being a scientist.   So here I am more than forty years later, no longer writing poetry, practicing a lot but not getting stoned, protesting the war but not getting thrown into jail and blessed with the result of the decision I did take.  In 1966 I decided to become a scientist since it did not require me to cut off my beard or shorten my hair.  Actually being a scientist, Hassidic Rabbi, jazz musician or war protestor were very consistent with the way I looked (remember this was San Francisco in the 60s).  Only problem was that I never went to University (I went to sea as a merchant seaman instead).  Now I am going to skip over a lot of stuff. I was doing research at the Langley Porter Institute at the University of Cal. Medical School in SF and around 1967 we got a PDP-7 from Digital Equipment Company to replicate some experiments that other researchers had already done.  By that time I had been designing equipment for EEG studies for Joe Kamiya (we did the first brain wave bio feedback work).  I used digital modules (R series) from Digital Equipment (by the way, I ended up running the low end hardware group of Digital many years later) these were plug in boards that had things on them like flip flops and gates.  Well in comes this computer. I did not know anything about computers per se.  That night I opened up the computer and found out that it was made up of the same kind of boards I was using.  But when I used these boards I connected them with actual wires through what was a called a plug board.  Well there was no plug board and I could not figure out how the different boards “knew” what to do.  I even had to read the manual and that is when I discovered software and I was rocked to my soul. Here is a photo of a PDP-7. pdp-7.jpg There were only 120 of them ever built.  They cost $72,000 in 1965.   The most important thing that happened on the PDP-7 was that it is Dennis Richie developed UNIX.  This computer had an 18 bit word length (which means 2 bytes plus two bits kiddies).  The memory cycle time was 1.75 microseconds.  It took 4 microseconds to add two numbers together.  I can’t remember how big the memory was but I could actually remember most of the content of the memory in my head (I was a lot smarter then).  You can see a bunch of switches in the photo.  One set was to establish an address and the other set was for the content.  The computer was so dumb when you turned it on that you had to put in a small program via the switches (called the Rim Loader).  That program was smart enough to read a paper tape program via the ASR-33 teletype.  asr33.jpg I bet we did not even have the equivalent of 8k bytes.  I learned to program it pretty well together with a friend named Pete Harris.  We would stay up all night getting that computer to do things that Microsoft still has not figure out how to do. But most fun was programming the lights so that their turning on an off would create RF which we could pick up on an am radio.  We created music. Eventually we got a tap drive and we figure out how to program that so that we could make the cabinet in which it was housed vibrate in a way that looked like dancing and that we could sync to the music we made through the lights. Of course we only did this late at night since during the day we did real science like studying guys that were high on drugs or if we were lucky Zen Monks.

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