>>My understanding was that with Mach3, the THC up/down moves were done by the LPT driver.
They were. However, the spec of Mach4 was that such things were not to be done by the device. Darwin was completed long before Mach4
and to that original spec. There is no backlash or thc in Darwin. Darwin is at this point meant to be a bridge, it allows you to use Mach4 as
a printer port user, but its capabilities will never be increased, it is a basic 4 axis printer port driver that will do most things, but it wont
do THC, Backlash or threading.
Art