Taken from the MEL of a well known SE Asian airline who have operated up to fifty B747-400 aircraft:
For Category III operations all three must be operative.
For Category II operations one may be inoperative provided several engineering requirements are met, mainly concerned with pulling and collaring the inoperative FCC's FCCServo CBs, OR
To despatch with one or more inoperative (and that can be all three inoperative) then flight time must not exceed 3 hours and the aircraft can only be operated to Cat I limits, also inoperative FCC's FCC Servo CBs have to be pulled and collared.