Is this for use with steppers or servo's, as it is that Gecko usually closes the servo loop via encoders?
When true closed loop servo boards are used, the PID servo loop is done in the card, so there would be a conflict if Gecko attempted the PID loop also.
Unless the card just operates as closed loop monitor and compares the Mach command to the actual position within the PC.
Normally with Mach and Gecko/encoder drives, Mach does not know of any position error that might occur.
The board could also be used to monitor stepper error and advise mach through the PCI interface of excess following error?