Haha, your feelings again mactec. The UC400ETH is a whole better than the Smoothstepper, it works with 3 softwares (Mach3, Mach4, UCCNC) and works flawless.
So he can upgrade any time to mach4 when he wants with the UC400 or even better if he upgrade to UCCNC as it is superior to Mach XY.
It is funny that for you everything is better than what I say, just because I'm saying it.
Step/dir or Quadrature driven servos often have MHz step rates to get high speed and resolution
For example if you had a 20000 step/turn servo, 3000 RPM would requite a 1MHz step rate.
These signals are usually conveyed with differential signaling for noise immunity.
Higher step rate capability also suggests a cleaner step signal as the jitter and beats
of the step rate against the fundamental clock rate are reduced.
For example, our step-generators can generate steps to 10 MHz and have a base clock of 100 MHz...
The time base of 400kHz is 2.5 microseconds, I don't think that a cleaner step signal is needed than that.
MHz signals are very short needle like pulses I would not run my system with that fast signals but ofcourse everybody do what they want to, it is not my problem.