Even Older Man Yells At Whippersnappers
On Wed, Sep 20, 2017 at 5:09 AM, Gregory Ewing
<greg.ewing at canterbury.ac.nz> wrote:
> Never mind that fake assembly rubbish, learn a real assembly
> language! And hand-assemble it and toggle it into the front
> panel switches like I did!
1979, I was working at Bausch and Lomb in Rochester NY. We had a 16
bit Data General Nova 'Minicomputer'. It had 4 registers, called
accumulators. It had 16 front panel toggle switches, one for each bit,
one that said 'deposit', and one that said run. It had a dial with
stops for AC0, AC1, AC2, AC3 (for the 4 accumulators), PC (program
counter), address and contents.
When you powered up the machine it did not boot. You had to hand enter
a short bootstrap program in binary. Do to this you had to turn the
dial to address, key in a 16 bit address, click deposit, turn the dial
to contents, key in a 16 bit line of assembly code, click deposit, and
repeat this for each line of code (there were like 5 or 6). Then key
in the address of where you wanted to run from turn the dial to PC,
deposit, and click run. Any mistake and it would not boot. Often took
3 or 4 tries.
After a few weeks of this I was sick of it. I had the boot code burned
into an EEPROM (which I had to send out to be programmed). Then I
build a very small wire wrapped board with the EEPROM and an
oscillator and few TTL chips. I tapped into the 5V power on the CPU
board and used the leading edge of that to trigger a one shot which
'woke up' my circuit, and caused it to clock out the code from the
EEPROM and load it to the appropriate place, set the program counter
and start the program. I drilled holes in the CPU board and mounted
this with little plastic standoffs.
I did this all on my own, coming in on the weekends, without company
approval, and when it was working I showed my boss. He was blown away
and he was sure we could patent this and sell it. He had me formalize
the design, write it up, have an actual PCB made, go to the company
lawyers, the whole 9 yards. Then Data General announced the new
version of the Nova .... with auto boot.