Deano, could I see your tool change atc macro? Mach 3
Also, which motion controller did you use? Plain old PP? ethernet SS? DSPMC? etc...
The reason being is that the closed loop DSPMC and CSMIO options dont rely on the windows jitter to make steps and dir for outputs....it does eveything on board, just like a normal industrial motion controller...
If your using Parallel port, thats where u are gonna have issues, even if you use usb or ethernet. Without a DSPMC or CSMIO, you kinda only relying on the computer... not the motion controller.