Also, it's important to remember that the Polysix has two CPUs: (1) the key assigner CPU and (2) the CPU that handles everything else (servicing all the push buttons and knobs, saving and recalling patches, etc).
The key assigner handles everything that's "fast". Primarily, it scans the keybed to look for which keys are pressed and then it continually updates the pitch CV to each of the six voices (multiplexed). It does this in a fast loop that cycles every 6 milliseconds or so. I replaced my key assigner CPU with an Arduino, so I had to reverse engineer most of its functions. You can read about its basic timing loop here:
The other CPU operates independently. It scans all the user controls (push buttons and knobs) and creates control voltages based on these settings in order to drive the synth voices. I don't know much about this CPU as it was far less interesting to me than the key assigner. Depending upon what you want to learn about, however, this might be exactly what interests you.
Hope that this helps,
Chip