[pups] Issues of AUUGN...

dmr at plan9.bell-labs.com dmr at plan9.bell-labs.com
Wed Oct 4 14:31:40 AEST 2006

Dave Horsfall mentioned, about some old editions of AUUGN,

 > It contains the famous Thrust Meter, a few papers by Yours Truly, and I
 > think it has the short assembly program that would bring a PDP-11/70 to
 > its knees (the infamous "SPL" firmware bug).

Was this the feature (not really a bug; it's in the manual)
that SPL suppressed interrupts for one instruction after the SPL?
I suppose it was indeed a bug that this happened even in user mode
where SPL was intended to be a no-op.

I remember trying this.  It depends on completely filling
memory with SPLs, which I could not figure out how to
do using an instruction sequence.  However, putting
a bunch of SPLs into a file and reading it in over the program
did the job.

It was a bit hard to break out of--the halt switch didn't work.
At first I thought that power-off was the only solution, but it
turned out that holding down both reset and halt simultaneously did
the job.


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