I remember being taken on a tour of one of my companies data centers in 1987 (I was a newly inducted Ops Staff on MVS systems, back then) and when walking past

I remember being taken on a tour of one of my companies data centers in 1987 (I was a newly inducted Ops Staff on MVS systems, back then) and when walking past an ICL mainframe, the guy showing us around pointed out a knob at the top of the casing; told us it was the volume control for a speaker. They used it to listen to the sound of the CPU (it was somehow wired up, I don't recall the specifics) and could tell if it had crashed or not. Anecdotally, this was not an unknown concept to me. As a teen learning assembler on early 80's Z80 machines, one could literally hear the CPU fizzing through loops, copies etc, if one listened closely enough (80's Z80's were not fast :) ) Using sound, for monitoring of distributed systems was a hack-day project at work a couple of years back, but sadly never went anywhere. I'd much prefer to monitor my systems through an audible interface than a visual one, but I wonder how much of that is connected to my having been interested in audio in general over the years (in the capacity of audio engineering, music etc)