I'd never seen that demo before, but from your description I had a suspicion it would be a C64 floppy drive, which has the same CPU as the C64 itself and runs e

I'd never seen that demo before, but from your description I had a suspicion it would be a C64 floppy drive, which has the same CPU as the C64 itself and runs embedded firmware acting more like a file server: https://en.wikipedia.org/wiki/Commodore_1541 https://en.wikipedia.org/wiki/Commodore_1541 https://en.wikipedia.org/wiki/Commodore_DOS https://en.wikipedia.org/wiki/Commodore_DOS