A substrate processing apparatus is provided. The apparatus has a casing, a low port interface and a carrier holding station. The casing has processing devices within for processing substrates. The load port interface is connected to the casing for loading substrates into the processing device. The carrier holding station is connected to the casing. The carrier holding station is adapted for holding at least one substrate transport carrier so the at least one substrate transport carrier is capable of being coupled to the load port interface without lifting the at least one substrate transport carrier off the carrier holding station. The carrier holding station is arranged to provide a substantially simultaneous swap section for substantially simultaneous replacement of the substrate transport carrier from the carrier holding station.