Can you describe such an implementation? Any idea of how the PPG machines implemented their oscillators? Any idea of the Prophet VS oscillators were free running or always in sync?
You'll find the most technological information about the PPG on Paul Maddox' PPG Webpages:
http://www.ppg.synth.net/wave22/I strongly assume that the playback of the waveforms on the VS just happened the way it does on the Evolver: 12-bit sample playback triggered by the keyboard or another modulation source.
Interestingly enough, the development of the VS was triggered by the PPG Wave. Chris Meyer, one of the product designers among Josh Jeffe, obtained one and took a look inside. He eventually came up with the cross-fading idea for which Josh Jeffe suggested the joystick as a controller.
Also interesting: The whole Arpeggiator Scratchpad idea that is found in the Prophet 12 and that allows you to insert rests, notes, and so on, stems from the VS's arpeggiator functionality.
As far as architecture and components go, I've attached an overview of the chipset from
The Prophet from Silicon Valley below.