CompactPCI

The connectors and the electrical rules allow for eight boards in a PCI segment.

[2] 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.

Some of the pins are slightly longer to provide proper grounding when devices are inserted and removed.

CompactPCI was initially ratified as PICMG 2.0 in late 1995 as a passive backplane for PCI signaling.

Originally designed to support the PCI signaling protocol (and hence the name "CompactPCI"), CompactPCI has grown to include a variety of technologies centered on the application of the 2mm HM connector on the 3U and 6U form factor.

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.