Null job light patterns? - test-drb@ccmp.vtda.org

31 Jan 2007

"J. Peterson" <pdp11 at saccade.com> wrote:

...
 >>   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

 1000000000000001
 1100000000000011
 1110000000000111
 1111000000001111
 0111100000011110
 0011110000111100
 0001111001111000
 0000111111110000
 ...
 with the groups of four "on" lights moving through each other. 
Correct.

...
   RSTS (c.
 1980) simply rotated half a dozen or so "on" lights. 
No no no. RSTS/E had a really cool pattern. They had two "snakes" 
running around across the data and address lights. That was a real 
trick. Appearantly they pulled that off by having the idle loop actually 
run in supervisor mode, which wasn't used by RSTS/E at the time, so they 
could control the address that way. Rumour have it that they had to drop 
that piece at RSTS/E V9 or if it was V10 when they finally started using 
supervisor mode more seriously in RSTS/E, but I haven't seen the RSTS/E 
idle loop since V8 so I couldn't really say.

...
   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?

I can't remember any idle pattern when running 2.11BSD on an 11/70 
anyway. The machine was idle sometimes, so maybe they just didn't 
implement anything fun. But I'm not entirely sure my memory is on par 
here. They might have had a simple rotating pattern on the panel. It's 
been a few years since I last fired up Unix on a PDP-11.

Other machines have probably also done idle patterns, but in the PDP-11 
rumour have it that the different OS groups were competing with each 
other on who could do the coolest idle pattern. I believe most agreed 
that RSTS/E won.

	Johnny