COM Express

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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.

History[edit]

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." [1]

Types[edit]

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:

  • Type 1: Single connector (220 pin), 6 PCI Express lanes, no PEG, no PCI, no IDE, 4 SATA, 1 LAN
  • Type 10: Single connector (220 pin), 4 PCI Express lanes, no PEG, no PCI, no IDE, 2 SATA, 1 LAN, single channel LVDS only, DDI, no VGA, 2 Serial COM
  • Type 2: Double connector (440 pin), 22 PCI Express lanes, PEG, PCI, 1 IDE, 4 SATA, 1 LAN
  • Type 3: Double connector (440 pin), 22 PCI Express lanes, PEG, PCI, no IDE, 4 SATA, 3 LAN
  • Type 4: Double connector (440 pin), 32 PCI Express lanes, PEG, no PCI, 1 IDE, 4 SATA, 1 LAN
  • Type 5: Double connector (440 pin), 32 PCI Express lanes, PEG, no PCI, no IDE, 4 SATA, 3 LAN
  • Type 6: Double connector (440 pin), 24 PCI Express lanes, PEG, no PCI, no IDE, DDI (for DisplayPort, HDMI, DVI or SDVO), 4 SATA, 1 LAN, 2 Serial COM, USB 3.0

Size[edit]

The specification defines 4 module sizes:

  • Mini: 55 × 84 mm (2.2 × 3.3 in); formerly known as nanoETXexpress
  • Compact: 95 × 95 mm (3.7 × 3.7 in); formerly known as microETXexpress
  • Basic: 95 × 125 mm (3.7 × 4.9 in); formerly known as ETXexpress
  • Extended: 110 × 155 mm (4.3 × 6.1 in)

Specification[edit]

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.

ETX XTX COM Express
Dimensions 95 × 114 mm (3.7 × 4.5 in) 95 × 114 mm (3.7 × 4.5 in) (ETX footprint)
  • 110 × 155 mm (4.3 × 6.1 in) (extended)
  • 95 × 125 mm (3.7 × 4.9 in) (basic)
  • 95 × 95 mm (3.7 × 3.7 in) (compact)
  • 55 × 84 mm (2.2 × 3.3 in) (mini)
Legacy1 support Full legacy Legacy except ISA Legacy except ISA
PCI Express support - 4 Lanes up to 6 Lanes (basic)
PCI Express Graphic support - - up to 16 Lanes
Ethernet support 10/100 10/100 10/100/1000
IDE support 2 IDE, 2 SATA2 2 IDE, 4 SATA IDE, 4 SATA
LPC support - yes yes
USB support 4 USB 6 USB 8 USB
Audio support Line In/Out, Mic AC'97, Line In/Out, Mic AC'97, Line In/Out, Mic, AC'97 digital, HDA
Power 5V, 5VSB 5V, 5VSB 12V, 5VSB
Notes:
  1. "Legacy" is defined as the older PC peripherals and bus, such as ISA bus, RS-232 serial, IEEE 1284 parallel, floppy, and PS/2 keyboard & mouse.
  2. ETX 3.0 adds SATA via a topside connector on the board.

References[edit]

See also[edit]

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