Computer

Pdp-11 and playing with printers

Last Updated or created 2022-11-27

I got a free mainframe, when i was about 17.
It was a huge Pdp-11/34 which a had to get from Enschede to Holten using a trailer.

PDP-11/34
  • It was a 19inch rack (loads of metal)
    • 2x 8inch floppy drives
    • 2x 20MB harddisk drives (with cardridge) each 34KG!
  • multiple (3?) Decwriter III printers
  • loads of VT100 terminals
  • 2.5 meter of manuals
  • cables
  • disks (8 inch) and harddisk cartridges

I converted the power to a generic 230V connector. When booting the machine all the lights in the house dimmed.

I didn’t know anything about mainframes, but i got things working.
Sometimes i would play with it, but after a while it didn’t run anymore.

I’ve kept some of the parts of the machine.
Terminals we used for a long time to connect to a linux server.
( The VT100 where later switched for more modern Wyse terminals )

One of the two drives (34kg) (not my picture)

Some parts i’ve kept

20MB cartriges for above drive
Magentic core memory!
16K x 12
VT100 serial terminal (gave this one to a colleage) Postit says: Could you install Windows on this for me??
Wyse 50 Terminal
Stallion Card to connect 8 terminals

Serial printer

Last Decwriter i’ve got, also gone now.

These printer we used for generic printing, and just for fun.
They made a lot of noise, and even they are serial printers they are fast!

So i resourced ms-dos into assembly and printed that, that was a sh*tload of paper.
We even made a racing game. (Can’t find the source, but i’ve recreated a lookalike in linux-bash)

Object of the game was to keep your car O character on the road.
The printer printed the lines, and you could use the keyboard to move your car, which also got printed.

Below the build-in-5-minutes bash lookalike. ( z left, x straight and c right)
Original had more intricate road, and probably the road was drawn using two lines, to speedup printing (Decwriter III could print at 180 characters per second bidirectional!)

Looked more like this i think
#!/bin/bash
i=0
j=0
car=8
while true ; do
no=$(awk "BEGIN{print sin($i*atan2(0,-1)/180)*40+40}" | cut -f1 -d.)
way=$(awk "BEGIN{print sin($j*atan2(0,-1)/180)*10+13}" | cut -f1 -d.)
#echo $way
if [ $car -lt 0 ] ; then echo "boom" ; exit ; fi
if [ $car -gt $way ] ; then echo "boom" ; exit ; fi
carr=$car
rest=$((140-$no-$way))
i=$(($i + 1))
j=$(($j + 5))
while [ $no -gt 0 ] ; do
echo -n " "
no=$(($no - 1))
done
echo -n "#"
while [ $way -gt 0 ] ; do
echo -n " "
if [ $carr -eq 0 ] ; then
echo -n "O"
fi
way=$(($way - 1))
carr=$(($carr - 1))
done
echo -n "#"
while [ $rest -gt 0 ] ; do
echo -n " "
rest=$(($rest - 1))
done
echo ""
read -r -t 0.1 -n 1 -s key
if [ "$key" == "z" ] ; then
car=$((car - 1 ))
fi
if [ "$key" == "x" ] ; then
car=$((car - 1 ))
fi
if [ "$key" == "c" ] ; then
car=$((car + 1 ))
fi
done