The SIRFIII chipset is strictly in the GPS receiver.
It enables the receiver to get a faster lock to satellites and triangulates your position faster and more accurately than older technologies.
It has nothing to do with the data that is output by the receiver. If the output from the receiver is NMEA sentences, then it will work correctly with FreeDrive, regardless of the chipset inside the receiver.
Have you looked in the FAQ yet?
How about the Wiki?
Under normal circumstances, a signature would go here.