A PCI mezzanine card or PMC is a printed circuit board manufactured to the IEEE P1386.1 standard. This standard combines the electrical characteristics of the PCI bus with the mechanical dimensions of the Common Mezzanine Card or CMC format (another IEEE standard). It enables manufacturers to offer products that are compatible with the well-established PCI bus, but in a smaller and more robust package than standard PCI plug-in cards. The word mezzanine, meaning an platform inserted between two floors of a building, describes the way in which a PMC card fits between two adjacent host cards in a standard card rack, attached to one of the cards by connectors and mounting pillars. A single PMC measures 74 mm x 149 mm. The standard also defines a double-sized card, but this is less common than the single card.
Carrier cards that accept PMCs are usually made in the Eurocard format, which includes single, double and triple-height VME cards, and compact PCI (cPCI) cards.
