MODCOMP II Rescue Revisited...

Lyle Bickley lbickley at
Mon Jun 4 23:06:56 CDT 2007

A number of you probably remember me "announcing" in Jan, 2007 that I had 
rescued a MODCOMP II/12 from a lab here in Silicon Valley. The link for that 
is below (sorry, it's slow - the pictures are large).

After a lot of work cleaning up both the CPU and I/O chassis I began checking 
out the system. It turned out that the I/O chassis was in pretty bad shape. 

I went back to the lab facility where I found the MODCOMP II - looked through 
several more buildings - and found another lone MODCOMP II I/O chassis. I 
went through the "salvage" process again - and finally picked it up about a 
month ago.

It was in a lot better shape than the original I/O unit. And the really great 
news - it was an identical configuration to my original I/O chassis.

After cleaning it up, doing all the usual capacitor, power supply checking - I 
powered it up - and everything "looked" good - and no bad "cooking" 
smells ;-)

I cabled up the CPU and I/O unit, powered 'em up - and to my amazement the 
front panel controls seemed to work O.K.

I then did the usual hand memory tests - and core memory worked O.K. every 
location I tested.

I then wrote a bunch of small diagnostics (in machine code) - and found that 
I/O was not easy to code - but I did enough to check that the console in/out 
ports worked O.K.

Today I loaded diagnostic monitors, and diags - and most of the system - 
including I/O is working! The really good news is that all 64K (words) of 
core memory passed the long manufacturing memory diagnostic - which even 
tests for "hot cores" failing.

It's been months in the making this critter come alive - but it sure feels 
great when the diagnostics tell you that you are on the right track :-)

Lyle Bickley
Bickley Consulting West Inc.
Mountain View, CA

"Black holes are where God is dividing by zero"

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