4 Oct
2006
4 Oct
'06
4:31 a.m.
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.
Dennis