Hi,
I suspect that by elevating the priority of Mach3 that it suffers less interruptions and therefore the UC100, or rather, the USB connection
to the UC100 runs better.
As a side note Windows makes such extensive use of the CPUs interrupt system that it cannot ever be 'realtime'.
It is this lack of realtime determinism that prevents Windows/Mach from being a feedback controller, Mach, in fact all
Windows based CNC software solutions, must be 'buffered'.
Compare that to LinuxCNC, it runs on a realtime capable distro of Linux and it can creditably be a feedback controller.
Craig