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 (IEEE 1386 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 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 rarely used.
A PMC can have up to four 64-pin bus connectors. The first two ("P1" and "P2") are used for 32 bit PCI signals; a third ("P3") is needed for 64 bit PCI signals. An additional bus connector ("P4") can be used for non-specified I/O signals. In addition, arbitrary connectors can be supplied on the front panel, or "bezel".
Carrier cards that accept PMCs are usually made in the Eurocard format, which includes single, double and triple-height VMEbus cards, CompactPCI (cPCI) cards and more recently, VPX cards.
AMP cards built onto the PMC mezzanine form factor include the H264-PMC8 Eight Channel H.264 Codec and H264-ULL-PMC Dual-channel PMC Mezzanine HD H.264 Encoder.