For those that have 'scoped the PWM signal, how much fluctuation was seen, either frequency or pulse width.
If so, at what set frequency?

Hi,
PWM stability is pretty good if you use an external motion controller like an ESS, but not so good with a parallel port.

PWM is handled by dedicated hardware with an external motion controller whereas a parallel port is relying on a interrupt driven timer.
Windows makes extensive use of interrupts for its internal use and consequently interrupt driven timers fare poorly.

Craig