On the CDC 3800, the top three bits of the accumulator were scaled and summed by a set of
three resistors, then fed into the console speaker. Generally, this produced noise of
very little interest (except to indicate that the machine was running).
However, when I ran my Shellsort (
https://en.wikipedia.org/wiki/Shellsort
<https://en.wikipedia.org/wiki/Shellsort>), the speaker made a very distinctive
sound. It was a series of rising tones whose durations got shorter and shorter.
Something like Vwooooooooooop, Vwooooooop, Vwooooop, Vroop, ...
-r