A310-300 & A300-600 = 2 AFCS systems each with a Command and Montitor channel. Ergo, Fail Operational/Fail Passive assured.
The purpose of multiple system:
1) To allow Cat 111 + autoland and redundancy
2) To give pilots something else to b*gger up
3) To give avionics engineers the ability defer stuff and still prevent the pilot from really flying the aircraft (lot safer that way).