A wafer processing system has a wafer loading system accommodating sufficient wafer carriers to substantially maximize the processing speed capability of the processing system. Wafer carriers are placed into and removed from the loading system by one or two overhead carrier loading tracks. Carriers may be loaded or removed while other carriers are in work. One or more transfer robots may move wafers from the carriers to buffers. One or more process robots in a process module move wafers from buffers, or other locations, to processors in the process module.