Hi Hunserv,

For the parallel port, the resolution of the PWM is the Mach3 kernel speed/PWM base frequency

So, if you have a Mach3 kernel frequency of 45KHz and a PWM base frequency of say 10Hz, then the resoulution of the PWM output is 45,000/10 = 4,500 steps between 0% and 100% of maximum speed. So that is 0.022%

Therefore if you have a maximum spindle speed of 10,000rpm, the speed resolution you can get is 10,000 / 4500= 2.22 rpm

For the smoothstepper, I'm not completely sure but I think that the equivalent value for the kernel speed is 4MHz so the resolution is a lot higher.

Cheers,

Peter.