So the filter on a SID is analog. Great.
What about the oscillators? Digital or analog?
If analog are they DCO or VCO?
I’ve always assumed they were digital but I’ve read otherwise…
Ta!
The oscillators are digital. Frequency is set by a 16-bit register, which is relative to the system clock (standard 1.0 Mhz). The waveforms are then generated by an accumulator, which produces the sawtooth waveform. Some other digital tricks are done to produce the other waveforms. In case you’re interested, here’s an article with Bob Yannes, creator of the SID: http://www.joogn.de/sid.yannes.html