Abstract: A media independent interface (MII) is utilized on each processor card of a multi-processor card system in a carrier sense multiple access/collision detection (CSMA/CD) standard bus configuration to provide a data communications bus. This permits standard Media Access Control (MAC) devices to be used with the MII. The collision domain is implemented by having each active processor card using the data communications bus assert an analog signal on a single conductor of the back plane and sense its voltage value to determine if one or more processor cards are currently accessing the bus.