Post #1581445

@infosecdj @RueNahcMohr This piqued my interest and got me wondering why a VFO (variable-frequency oscillator) would be used in a floppy controller. From what I guessed/researched, it seems that data tracks on the floppy surface are encoded at a fixed density. This would mean that tracks closer to the centre have less data compared to the outer tracks. Assuming a constant (or near-constant) angular speed, data from different tracks would be arriving at different rates. Based on this, the VFO has two purposes: synchronise a phase-locked loop to the particular track speed (based on special track markings)report the speed back to the controller so that it can read data at the correct rate That's really as far as I researched it. It may also be that finer adjustments to the data rate might happen during a track read? That would probably depend on the particular disk format and encoding used. I think the above is OK to a certain level of approximation. Please let me know if I'm wildly off the mark.