A complete computer on a single printed circuit board, including clock, microprocessor, RAM, flash memory, Ethernet and I/O controllers. Also called a "system-on-module" (SoM), a computer-on-module (CoM) may not have ports for peripherals as do single board computers. They often must connect to another board for pathways to the outside world.
ETX, XTX and COM Express
Embedded Technology Extended (ETX) provides a standard form factor for x86-based computer-on-modules and includes support for the older ISA bus. Express Technology for ETX (XTX) excludes ISA and adds four lanes of PCI Express. COM Express/ETXexpress supports 16 lanes of PCI Express for graphics and bumps Ethernet from 10/100 to 10/100/1000. See
single board computer.