OT: Old-Time Computer Experiences

[Jerry Davis]

I thought I would take this off-topic from the "Re: anyone around 18 in the 
group" thread:

In 1982, I was working for DEC in Dallas, when I got this phone call from a 
fellow DECee from Tulsa, who said it was my call, because Dallas was closer 
to Ardmore that to Tulsa. So I called him to see what we could do for him.

He was from a company called at the time "UniRoyal" and whenever I asked him 
what OS he was running he kept saying "I have a PDP-11/20". Well PDP-11/20's 
were waaaaaaaaaaaay out of service, having been superseded by different 
various models for years and years. (It turned out he had it installed in 
1970 with core memory, high speed paper tape punch reader, core memory and a 
snazzy asr33 with punch tape).

Anyway, it was money ..., so I drove up, and took a look at what he had and 
what he wanted to modify. Well I wound up staying there 12 weeks doing his 
modification.

This computer controlled making the "rubber" from raw ingredients. The rubber 
was made in a giant mixer, which was fed raw ingredients at specified times. 
The Computer would be fed a "recipe", and would control when the raw 
ingredients came into the mix, and in which order. My job was to add a 
temperature component to the program which would then be used as part of the 
recipe.

Two very funny incidents happened while there though, that I want to share 
with you.

1. After pouring through the 90 paper tape listings that he had (it was all 
assembly language [ including the floating point code, which would be later 
put into a chip and called the FPU ]), I declared that I might be able to do 
the modification for him, but that I needed 4 more Kwords of memory to do it 
in (since there WAS no disk - just core). He said fine. He swivelled around 
in his chair picked up something that looked like it ought to go into the 
unibus backplane, and was about 16" W x 14" H x 3 " D, with about 15 14" x 
3" cards in there (that you could see every resistor, diode etc. on the 
card) and heaved it on the desk in front of me. I asked him what that was, 
and he said "4K memory". I just about died laughing on the spot.

2. After I was 8 weeks into the project (adding temperature to the equation), 
I was in "test" mode. I added 2 paper tapes to the system, with my code, and
In analysing the code, I thought I had picked an unused address to stick some 
temp data for my calculations. Well ... it turned out that another part of 
the program was using that for a tempory "subroutine" that was created and 
then called. Well you can imagine the result. I was stomping all over this 
subroutine with my data, so everytime the other part of the program would 
call this address, (where I had chosen to put my data), it would invariable 
see a octal 0 there, and would IMMEDIATELY halt (as an octal 0 is a halt 
instruction in the PDP instruction set). As the only time I could "test" 
this puppy was during live time, and as there was a "offline switch board" 
if the computer went down. The operators were not happy seeing me.

It got so, whenever I came into the room with my tray full of paper tapes, 
which was maybe once per day, when I fed my paper tape into the system, all 
the operators would get up, and stand by the offline switch board "at the 
ready" for when the computer would halt. Oh by the way, if that wasn't bad 
enough, when the computer went down, it caused a red light and siren 
mechanism to go off to alert the operators.

I did find out why it was halting, and got it to work, and the operators were 
glad to see me go!

I still have the first piece of test rubber and the paper tape binary from 
that run.

Jerry 
-- 
Registered Linux User: 275424
Today's Fortune: Hey, Jim, it's me, Susie Lillis from the laundromat.  You 
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gonna call and it's been two weeks.  What's wrong, you lose 
my number?