PDP-1 project milestone

Lyle Bickley lbickley at bickleywest.com
Wed Mar 2 01:59:43 CST 2005

It was indeed thrilling to play Spacewar tonight on the PDP-1 - although I 
have to admit I was one of the team members who wanted to stop at the very 
positive note of having fixed the left shift/rotate bug - It was getting late 
and I was worried that Spacewar wouldn't run - and we'd have to leave tonight 
feeling slightly discouraged...

I had played Spacewar in the early sixties at Stanford University and  many 
years later (in the mid-70's) I ran Spacewar on my own PDP-12.  But seeing it 
run tonight on the PDP-1 was amazing and exciting - a forty year old machine 
playing a spacewar game on a persistance-seven-screen was a sight to see and 
a great experience to feel!!!!!  It, for sure, makes all the hours of labor 
and TLC spent on the PDP-1 worth it :-)


On Tuesday 01 March 2005 22:53, Eric Smith wrote:
> The PDP-1 Restoration Project is still far from complete, but we hit
> a major milestone tonight.  When we last tried to run Spacewar,
> the sun and player ships would not display correctly, though the
> starfield and torpedos seemed to be fine.  We ran the DEC instruction
> diagnostics and they failed on the shift/rotate test, though all
> the diagnostics had passed a few months earlier.
> This week we wrote a more specific diagnostic program and determined
> that left shifts and rotates of the I/O register were not doing anything,
> though right shifts and rotates of the I/O register were fine, and all
> shifts and rotates of the accumulator were fine.  After a little study of
> the print set, we identified two system modules that could cause the
> observed behavior.  We tried replacing one of them, a 1607 pulse amplifier.
> After replacing the 1607, our own diagnostic and the DEC diagnostic
> both passed.  Some of the team wanted to go home without trying out
> Spacewar, but the rest of us nagged until they gave in.  We loaded it,
> and it ran correctly.
> Spacewar on the real Type 30 display with long persistence phosphor
> is a thing of beauty!
> Some of the tasks remaining to be done:
>      * build new Spacewar control boxes
>      * continue repair/testing of Soroban console typewriter
>      * adjust Type 30 display to factory specs (linearity is poor)
>      * adjust paper tape reader sensitivity/threshold
>      * diagnose & repair suspected flaky memory "module" 0
>      * voltage margin checks, run all diagnostics
>      * install new belt and test BRPE tape punch
> Eric

Lyle Bickley
Bickley Consulting West Inc.
"Black holes are where God is dividing by zero"

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