Editing PCI Mezzanine Card

{{Short description|Printed circuit board assembly manufactured to the IEEE P1386.1 standard}}
{{more references|date=June 2015}}
A '''PCI Mezzanine Card''' or '''PMC''' is a [[printed circuit board]] assembly manufactured to the [[IEEE]] P1386.1<ref>{{Cite journal|date=August 2001|title=IEEE Standard Physical and Environmental Layers for PCI Mezzanine Cards: PMC|journal=IEEE STD 1386.1-2001|pages=1–14|doi=10.1109/IEEESTD.2001.93279|isbn=978-0-7381-2830-6 }}</ref> standard. This standard combines the electrical characteristics of the [[Peripheral Component Interconnect|PCI]] bus with the mechanical dimensions of the Common Mezzanine Card or CMC format (IEEE 1386 standard).<ref name=":0">{{Cite book|language=en-US|doi=10.1109/IEEESTD.2001.93280|isbn=978-0-7381-2829-0 |title=IEEE Standard for a Common Mezzanine Card Family: CMC }}</ref>

A '''mezzanine connector''' connects two parallel printed circuit boards in a stacking configuration. Many mezzanine connector styles are commercially available for this purpose, however, PMC mezzanine applications usually use the 1.0&nbsp;mm pitch 64-pin connector described in IEEE 1386.<ref name=":0" /> 

A PMC can have up to four 64-pin bus connectors. The first two ("P1" and "P2") are used for 32-bit PCI signals, and 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 of the chassis or case, also known as a "bezel."<ref name=":1">{{Cite web |last=Gipper |first=Jerry |title=VITA - PCI Mezzanine Cards |url=https://www.vita.com/Hall-of-Fame/6873011 |access-date=2025-05-20 |website=www.vita.com}}</ref>

The PMC standard defines which connector pins are used for which PCI signals; in addition, it defines the optional 64 "P4" connector pins for use of arbitrary I/O signals.<ref name=":1" />

It enables manufacturers to offer products compatible with the well-established PCI bus, but in a smaller and more robust package than standard PCI plug-in cards. The word [[Mezzanine (architecture)|''mezzanine'']], derived from the Italian mezzanino and also commonly used to refer to a platform inserted between two floors of a building, describes the way in which a PMC 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&nbsp;mm x 149&nbsp;mm. The standard also defines a double-sized card, but this is rarely used.<ref>{{Cite web |title=PMC / XMC |url=https://www.ampltd.com/pmc-xmc/ |access-date=2025-05-20 |website=Advanced Micro Peripherals - PC104, miniPCIe, CompactPCI Serial, XMC, VPX - Frame Grabbers, Codecs, Video Streaming, Signal Conversion |language=en-GB}}</ref>

Carrier cards that accept PMCs are usually made in the [[Eurocard_(printed_circuit_board)|Eurocard]] format, which includes single, double, and triple-height [[VMEbus]] cards, [[CompactPCI]] (cPCI) cards, and more recently, [[VPX]] cards. One PMC fits on a standard [[Rack_unit|3U]] carrier card while [[Rack_unit|6U]] models (typical for [[VMEbus]] cards) can carry up to two PMCs. PMCs were also used in early ATCA systems before the advent of the [[Advanced Mezzanine Card]] or AMC.

For the PMC standard, I/O technologies account for much of the market, but various card functions are commercially available, including Intel architecture and PowerPC processors, graphics cards, and memory cards. I/O cards are available such as [[serial communication]] controllers, [[SCSI]] controllers, [[graphics controller]]s and [[FireWire]] controllers.

==Variants==
Additional standards exist that define variants of the standard PMC. For example,
* PMC-X ([[PCI-X]] PMC) defined by the [[VMEbus|VITA]] 39 standard
* PPMC (aka PrPMC; processor PMC) is defined by the VITA 32 standard. I.e. for allowing processors to have host or monarch support on a PMC. Additional signaling is defined so that the PrPMC can work as the host processor on a PCI bus. The intention is to allow a monarch PMC to control the PCI bus. This is usually a requirement if the PMC is to act as a host processor module.
* CCPMC (conduction-cooled PMC) defined by the VITA 20 standard
* XMC, or Switched Mezzanine Card (PMC with high-speed serial fabric interconnect) defined by the VITA 42 standard. XMC specifies a fifth connector ("P15") that supports [[PCI Express]] (VITA 42.3) or other high-speed serial formats such as Serial [[RapidIO]] (VITA 42.2) and Parallel [[RapidIO]] (VITA 42.1).
*[[FMC – FPGA Mezzanine Card]] provides a standard mezzanine form factor that offers a flexible, modular I/O interface to an FPGA located on a host system baseboard or carrier card.
* OAI-OAM (Open Accelerator Infrastructure - Accelerator Module) standard from [[Open Compute Project]], describes AI accelerator cards for blade servers, up to 8 cards on a universal base board, each with 7 PCIe x16 links, 12 V or 48 to 60 V power line, up to 600 W TBP (total board power) with air cooling, 600+ W with liquid cooling, interchangeable heatsinks and coldplates.<ref>{{cite web | url=https://www.opencompute.org/projects/open-accelerator-infrastructure | title=Open Compute Project }}</ref>

==References==
<references />

==External links==
* [https://web.archive.org/web/20110711103734/http://www.gocct.com/products/pmc_xmc/pmc_information.htm The PMC Standard] 
[[Category:Motherboard expansion slot]]