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Saturday, July 4, 2020

Old Computers


LCM+L PDP-7 booting and running UNIX Version 0

When I was studying Computer Science at The University of Texas in Austin, I had one class where we were allowed to use a PDP computer that was normally reserved for graduate students. The professor who was in charge of it gave a group of us a 30 second instruction on how to boot the machine: flip this switch, flip that switch, and then push the go button. Great, that explains nothing. WTF are all these switches and why does this sequence work? It was rote memorization and my mind balked. I caught him later on and asked him to repeat these instructions and he gave me shit for not paying attention the first time. Effing jerk.

I don't recall what I did with the machine, it was probably just an exercise to familiarize us with working with actual hardware. Everything else we did was done at an arm lengths remove from the giant fricking CDC machine via punch cards and printouts. There was one graduate student there who was mucking about with something and he discovered an undocumented opcode. He played with it for a bit and finally concluded that it was 'jump random and destroy' which doesn't sound particularly useful.

TI-990 Front Panel
My first job out of school was working with a Texas Instruments DX-10 mini computer (TI-900 was the computer, DX-10 was the operating system). It had a bank of front panel switches much like the ones in the video above. We actually used them a couple of times, but it was such a slow tedious process that almost any amount of software contortions were preferable.

IBM Channel Cable
We needed to hook it up to an IBM tape drive (I think it was an IBM, it used those frigging giant IBM channel cables). It wasn't too difficult, just a matter of figuring out which plugs to use and setting some jumpers, but I seemed to be the only one in the shop that could figure it out. I remember thinking the connector was pretty weird because the cable itself was this thick, armored thing about an inch in diameter, but at the end the sheathing had been stripped away and the connector was just hanging on a bunch of loose wires. Alien tech, but it worked.

Via Stu

3 comments:

Eck! said...

PDP computer is redundant. DECs usage was Programmed Data Processor, computer
is the same thing. As an owner of PDP-8f, several PDP-11 series machines and
being an ex digit (ex Digtial Equipment Corp engineer), its a thing. The
PDP-8f and PDP11s are all operational.

I also know that TI990 system. Didn't like it much.

Back in the late 70s specifically early 1979 I took data structures
in Pascal course at SUNY. My fun was when it came to the course work
the card deck (029 punch IBM cards) and printout from the Univac 1108
were the hand ins. Classic computer behind the glass wall. First day
after hearing that I stuff the hand in the air and ask, Can I use my
own machine? The professors dead stopped on that to asked "What?"
So I explained I have a Z80 based system with disks and ran UCSD
Pascal P system that was very complete language sensitive editor,
debugger, compiler in a unified system what we would call an IDE.
So after explaining it was real Pascal I was invited to bring the
system in. After showing its use I became very popular. This is
back when where a screen oriented editor [like we are used to here
and now) was nearly unheard of. Not having to punch cards, submit,
wait, and revise and correct it was easier to edit compile and
correct faster by 10 fold or more.

Modern kids assume a 486/DX66 is an antique and a 8088 based
system is unheard of.

Old computers still work and often urn up still doing their jobs.

Eck!

Chris said...

I love old computer talk. I would like to share a similar story. In 1977, I was offered a one-year assignment at the IBM lab in Kingston NY. Since I was from Canada, I was given an L1 visa. My wife did not have a visa and could not work, so she went to Duchess County Community College and took a 1620 Assembler Language course, just for the diversion. She was showing me her printouts one evening and, as you said, it was based on punching her code into punch cards, a very tedious and error-prone process. So I invited her to my office one evening (I was working a lot of overtime) and showed her how to use the VM/360/CMS on-screen editor. It was crude by today's standards, running on a text-only (green characters) 3270 display terminal, but you could fix a typo without having to punch another card. She was able to crank out a ton of code, including copious comments, in a fraction of the time required to produce a handful of punched cards on a keypunch. Of course, I did not have access to a 1620 assembler, or a 1620, so she still had to compile and run her code at school, but I did have a high-speed card punch. So, instead of showing up to class with a deck of 20 cards, she'd have a deck of 100 cards. And her program listings actually looked kind of professional.

Chuck Pergiel said...

Did you notice they are using the 'B' compiler in the video?