Software bus bridges (410.xy) are ordered in an order of associated bus identifiers (B), to allow programs accessing the corresponding physical bridges (310.xy) to find the correct software bus bridge either based on the bus identifiers, in which case the particular ordering of software bridges is unimportant, or based on the order of the software bridges. In some cases, this facilitates software porting across platforms with similar programmatic interfaces to the physical bridges but with different bus identifier ranges associated with physical bridges or with programmatic interfaces. A procedure is provided for determining the correct software bridge from a bus identifier. Other embodiments are also provided.