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

Paul Koning paulkoning at
Wed Jul 15 12:35:53 CDT 2015

> On Jul 15, 2015, at 1:28 PM, Noel Chiappa <jnc at> wrote:
>> From: Sean Caron
>> Many examples of blinkenlights eye candy throughout computer history
> 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.

I can see several reasons for the disappearance of console lights.  Cost, of course.  The fact that it wasn’t important for people running turnkey applications, i.e., much of the customer base.  And the switch from assembly language to higher level languages.

Then there was the very occasional early machine with no lights at all — the CDC 6000 series is the one I can think of.  But there you had the real time console status display, which was even better — updated just as fast but with a whole lot more information.


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