Reproducing old machines with newer technology (Re: PDP-12 at the RICM)

Jay Jaeger cube1 at
Wed Jul 15 13:11:51 CDT 2015

I remember when U Wisconsin ECE got their PDP-11/20 and I saw DOS
FORTRAN get stuck for the very first time.  I told the more senior
student who was responsible for getting things going, preparing
documentation, etc. that the machine was in a loop, and never coming
out.  He laughed at me, claiming there was no way I could know that.
Bzzzzzt.  Wrong.  Tee Hee.  That machine is now in my personal collection.

(PDP-11 DOS tended to scramble file system links and get stuck like that
- which inevitably required reloading the operating system disk - an
RC11 that still ran just fine when I last spun it up a year or so ago).

On 7/15/2015 12:35 PM, Paul Koning wrote:
>> It wasn't _just_ eye candy; it was a real help in problem debugging (when the
>> machine was stopped), and you could tell a lot about what the machine was
>> doing (when it was running) from the way the lights changed.
> Absolutely.  When DEC introduced the Remote Diagnostic Console for the 11/70, they started deploying those internally.  That makes sense.  But in the RSTS/E development group, we put our foot down and told them “take it out and give back our blinkenlights” because for OS development the ability to judge what the machine is doing, or spot strange behavior, from the light patterns is quite important.
> 	paul

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