Abstract: An apparatus and method for simulating a substrate being polished in a multiple carrier head per platen station when no substrate is provided in one or more of the multiple carrier heads is described. In one embodiment, a method for processing a substrate includes providing a single substrate to a polishing station adapted to process a plurality of substrates on a single polishing pad using at least a first carrier head and a second carrier head, retaining the single substrate in the first carrier head while the second carrier head remains substrate-free, urging the first carrier head and the second carrier head toward a polishing surface of the polishing pad; and providing relative movement between the polishing pad and the first carrier head.