COM Express, a computer-on-module (COM) form factor, is a highly integrated and compact PC that can be used in a design application much like an integrated circuit component. Each COM Express Module COM integrates core CPU and memory functionality, the common I/O of a PC/AT, USB, audio, graphics (PEG), and Ethernet. All I/O signals are mapped to two high density, low profile connectors on the bottom side of the module.
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History
The COM Express standard was first released in 2005 by the PCI Industrial Computer Manufacturers Group (PICMG) and it sought to provide standardized module interfaces for several different target applications. It did so by defining five different module "Types" each implementing different pinout configurations and feature sets on one or two 220-pin connectors. In that way, COM Express is a standard of multiple standards. It also defined 2 module sizes (later expanded to 4) to allow additional flexibility to better serve the end application while maintaining compatibility within each module "Type."
Types
There are 7 different pin outs defined in the specification. The most common used pin out is type 2. The latest pin-outs added in the revision 2.0 of the COM Express specification (available from www.picmg.org) are Type 6 and Type 10.
Maximum available interfaces for the defined types:
(*1) Option on previously allocated SATA2 and SATA3 pins. Implementor specific.
(*2) DDI can be adapted to DisplayPort, HDMI, DVI or SDVO in the carrier board.
Size
The specification defines 4 module sizes:
Specification
The COM Express specification is hosted by PICMG. It is not freely available but may be purchased from the PICMG website.
The current revision 2.1 (PICMG COM.0 R2.1) was released in May 2012. The original revision 1.0 was released July 10, 2005.