Where Do Interrupts Happen? (2019) (travisdowns.github.io)

I worked on an early 1970s computer with out-of-order processing. I got an interrupt due to a faulty instruction which caused a core-dump (aka a huge pile of paper containing a memory printout delivered by a very angry machine room operator). The message was that the failure occurred sometime in the last 16 instructions... which could have been branches from anywhere.

The only effective debugging technique was omphaloskepsis.

Sigh.