I had my first programming experience in the late 80s / early 90s on a Schneider (Amstrad) CPC 464 in Basic.
I remember that when a program was running, depending on the current workload of the processor you could hear a faint buzzing sound from the integrated speakers.
Especially when an empty
for loop was running (like
for i = 1 to 500 : next) which was regularly used to get short waiting times (as there was no
sleep command IIRC), you could hear this buzzing which gradually changed its frequency during the loop.
My question is: Was this a feature (as an audible feedback that the computer was working) or a consequence from insufficient decoupling of circuits?