The versions of bgminer 3.9 in MacMiner and available here:
have been updated to allow over clocking of antminer ASICs. To over-clock, open FPGA/ASIC window miner settings panel and put
--set-device antminer:freq=0781
in the manual flags text field, where 0781 is the default frequency, try replacing with 0881 or 0981 to increase your hash rate but make sure to cool your miners well!