A semiconductor processing system comprises a first, a second, and a third process module assembly. The third process module assembly is between the first and the second process module assemblies, and includes an opening for providing substrates to be processed in the various process module assemblies. The process modules are arranged laterally relative to the opening. The first and second process module assemblies each include an associated transfer chamber, an associated substrate transfer device, and a plurality of associated process modules attached the associated transfer chamber. The third process module assembly may include an associated transfer chamber, an associated substrate transfer device, and a single associated process module attached to the associated transfer chamber. The processing system is configured to sequentially load substrates into the process module assemblies neighboring the third process module assembly, and lastly load substrates into the process module of the third process module assembly.