CompactPCI

thumb|300px|A 3U CompactPCI backplane with J2 (top) and J1 (bottom, with blue key in the middle) connectors. The 32-bit PCI bus is carried on the J1 connector, while the J2 connector pins pass through to another connector on the back. CompactPCI is a computer bus interconnect for industrial computers, combining a Eurocard-type connector and PCI signaling and protocols. Boards are 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.

Unlike the original Eurocard solutions such as VME, which use connectors with a 0.1 inch (2.54 mm) pin spacing, CompactPCI cards use metric connectors with a 2-millimeter pin spacing, designed to the IEC 1076 standard. 3U boards have a 110-pin connector (J1), which carries the 32-bit PCI bus signals, and an optional 110-pin connector (J2), which carries either user-defined I/O or the upper 32 bits of an optional 64-bit PCI bus. 6U cards have an identical J1, a J2 that is always used for 64-bit PCI, as well as J3, J4, and J5 connectors for a variety of uses either as user-defined I/O or specified signaling such as Telephony and/or Ethernet signaling. Hot-plugging is a supported feature of CompactPCI. Some of the pins are slightly longer to provide proper grounding when devices are inserted and removed.