The multiplexers 60 a-60 i each receive nine inputs including four inputs from the coupled memory devices mem0-mem3, one input from the global port, and three inputs from the coupled processors on lines Px, Py and Pz, and one input from either the IOP (if the device associated with the SIB is a processor) or from another processor (if the device associated with the SIB is the IOP) on line PW/IOP.