thor44 wrote: the c10s and c10 boards are the same boards with the exception of the connectors for the wires.
do you think a pci parallel port card could fix the problem?
Sorry I didn't read your first message closely enough, and missed that you were using a breakout board.
The next thing to look at is step timing. The step space timing and step hold timing are going to be the ones to concentrate on. These can also be affected by the computers latency. If your timing is marginal differences the latency could push it over the edge and cause missed steps on one machine and not the next.
What stepper drives are you using? and what were the step timing settings you chose? If you choose settings that were equal to the drives minimum timings, it might be a good idea to add a safety margin (a 25% increase should usually be enough.)
