Hi,
at the current time there are about six manufacturers of external motion controllers that work with Mach4, that is to say thaey have a plugin that
is compatible with Mach4 and their board. Most of thise boards also have a plugin for Mach3 as well. If you are lucky enough to have one of
those boards then 'yes the same controller will work with either Mach3 OR mMach4'. If you have a yet different
controller then 'no, your Mach3 controller cannot be used with Mach4'
Craig