By providing an overhead buffer system between an automatic transport system and a load port assembly of a process tool, the efficiency of the respective load ports may be significantly enhanced, for instance, by reducing the idle time of empty carriers, thereby providing the potential for covering a wider range of operational scenarios compared to conventional strategies. For instance, for the same number of load ports, the overhead buffer system may provide a continuous operation, even if small lot sizes are used. The buffer system may comprise a dedicated transport mechanism for directly serving the load ports and respective buffer places, while respective transfer places may provide direct interaction with the automated transport system.