Null job light patterns?

J. Peterson pdp11 at
Tue Jan 30 15:01:44 CST 2007

>   I believe some of the -11 operating systems would do "interesting" things
>with the console lights while they were idle.  Could somebody describe the
>patterns used?

I seem to recall RSX had a pattern something like

with the groups of four "on" lights moving through each other.  RSTS (c. 
1980) simply rotated half a dozen or so "on" lights.  Others have described 
RT11's pattern.  I never saw a light pattern on an '11 running Unix - 
perhaps they were never idle?  Was the concept of the idle-loop lightshow 
unique to the PDP-11, or did other systems with data lights implement them?

In high school I had a Sol-20, and I missed the "blinkenlights" so much 
that I cut away a strip of metal in the top of the case (near where the 
"Processor Technology" logo was) and mounted a set of LEDs on perfboard 
behind it.  I sawed off the edge connector to a S-100 prototyping card and 
put it in the card extender slot at the top of the SOL's card cage, and ran 
wires from there to the perfboard.  By changing the keyboard input loop to 
repeatedly access various addresses, I was able to get a reasonable 
emulation of the PDP-11 lightshow in the address lights.

Decades later, I finally have a real '11 console to run the lightshows!


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