Fragmented backplane system for I/O applications

The present invention relates generally to "backplanes" (a/k/a "mother boards") into which a plurality of individual printed circuit boards can be plugged, and more particularly to an improved backplane structure allowing a very large number of interconnections between the individual printed circuit boards and the backplane. A backplane system allowing a very large number of interconnections between high-connectivity printed circuit boards and a backplane is disclosed. The backplane is fragmented into a plurality of backplane parts that comprise connectors on their edges to mate connectors arranged on the high-connectivity printed circuit boards. These backplane parts may also include other connectors on their edges to couple to extension printed circuit boards requiring less interconnections or cables. Interposers can be used to link several backplane parts and provide enhanced air circulation.