The smoothstepper is a USB device. It does away with the need for the parallel port but also it does away with the software pulse engine. This makes for a really clean pulse and at the moment it is at a Max of 4MHz, but I believe it possibly may be more in the future if needed. As I said I am one of the Beta testers of the SmoothStepper board and so far there have been a few problems but they have all been fixed, Greg still has a few things to add to the SmoothStepper such as spindle synchronisation but that should be done shortly.
The beauty of the SmoothStepper is it will allow people with LapTops etc to run Mach, as an example I tried this Pico board with the Mach DriveTest and although the pulse was very clean it crashed after about 30 seconds, with the smoothstepper the pulse is created outside the computer so there is no problem, even up to the 4MHz mentioned above.
Hood