The FASTBUS Segment Interconnect provides a communication path between two otherwise independent, asynchronous bus segments. In particular, the segment interconnect links a backplace (crate) segment to a cable segment. All standard FASTBUS address and data transactions can be passed through the SI, or any number of SI's and segments in a path. Thus systems of arbitrary connection complexity can be formed, allowing simultaneous independent processing, yet still permitting devices associated with one segment to be accessed from others. The model S1 segment interconnect being built at the University of Illinois supports these and other important features.