System for reformatting a response packet with speed code from a source packet using DMA engine to retrieve count field and address from source packet

A high performance serial bus operating at multiple transmission rates is disclosed. The serial bus is able to automatically generate data response packets for return to a requesting node. The automatic packet generation uses the source and destination information to generate a return destination packet for directing the requested data to the request source destination. Since the bus network is capable of operating at several different transmission rates, the speed at which the data request packet was transmitted is used for retransmitting the data requested back to the source node requesting the data.