CompactPCI

CompactPCI is a computer bus interconnect for industrial computers,combining a Eurocard-type connector and PCI signaling and protocols. Boardsare standardized to 3U or 6U sizes, and are typically interconnected via a passive backplane. The connector pin assignments are standardized by the PICMG US and PICMG Europe organizations. The connectors and the electrical rules allow for eight boards in a PCI segment. Multiple bus segments are allowed with bridges.

For more information, see Wikipedia.