Mezzanine card

Mezzanine is a term used to describe the stacking of computer component card s into a single card that then plugs into the computer bus or data path. The bus itself is sometimes referred to as a mezzanine bus. The term derives from the Italian word, mezzano , which means middle. The more common use of this term is in architecture, where it is a low-ceilinged story between two main stories in a building. In theaters, a mezzanine is a balcony projecting partly over the ground floor below it.

A mezzanine card is a smaller form of the more familiar Peripheral Component Interconnect ( PCI ) or Industry Standard Architecture ( ISA ) card. The original and still most popular mezzanine card is the Industry Pack (IP) card. An IP card provides a 16-bit data path. The IP card is 3.9 x 1.8 inches and has two 50-pin connectors that plug into an IP-to-PCI adapter card. The IP-to-PCI adapter card usually holds up to three IP cards. Another popular mezzanine card is the PCI Mezzanine (PMC) card. This card provides 32 or 64-bit data paths and uses 64-pin connectors. Both types of mezzanine cards are widely used with VME bus , which is an expansion bus technology that supports up to 21 cards on a single backplane . VME bus is widely used in industrial, telecommunication, and military applications.

A printed circuit board that plugs directly into another plug-in card. For example, a mezzanine card, also known as a "daughterboard," might plug into a VMEbus card, CompactPCI card or PCI card in order to extend its functionality. Adapter cards are also available that enable a mezzanine card to plug into the larger slot of the target bus.

Smaller than standard expansion cards, mezzanine cards are typically designed for rugged industrial use and are often bolted down after being plugged in. IndustryPack, PMC, PC*MIP and PC/104+ are commonly used mezzanine cards. See IndustryPack, PMC, PC*MIP and PC/104.