CAT would have been AMSDOS, not CP/M (it was DIR in CP/M). Not sure what was happening in that case though - it sounds like a bug, but not one I ever recall encountering!
Oh interesting. I swear it was cp/m; cat I’m more hazy on (though I feel like I didn’t use dir until ibm dos).
I had to really hammer on the command, and it would actually be trying to read either the hardware. I wonder if it was actually a physical issue that triggered it.
Sounds like whatever check that was used to determine whether a floppy was present or not had some small probability of giving a false positive. Maybe because without a floppy, the head would read random data that could pass some integrity check by chance.
