An island-based network flow processor (IB-NFP) integrated circuit has a high performance processor island. The processor island has a processor and a tightly coupled memory. The integrated circuit also has another memory. The other memory may be internal or external memory. The header of an incoming packet is stored in the tightly coupled memory of the processor island. The payload is stored in the other memory. In one example, if the amount of a processing resource is below a threshold then the header is moved from the first island to the other memory before the header and payload are communicated to an egress island for outputting from the integrated circuit. If, however, the amount of the processing resource is not below the threshold then the header is moved directly from the processor island to the egress island and is combined with the payload there for outputting from the integrated circuit.