[Greg McKaskle]

I think your PID loop will generally be limited by how often you can update your motor controller. For PWM, that is every 5ms for newer ones, 10ms for some older ones. CAN may be used to do faster updates.

The calculations are small by comparison. Of course you may not need to run your loop even that fast. It depends on the inertia of your system, the torque or force of the actuator, the lag of the sensor, etc.

Anyway, my point is that the 20ms is not a technical limit of the cRIO or roboRIO, but may be the default of the library you are using.

Greg McKaskle