What is a form factor (motherboards)?
This article compares the IBM compatible personal computer motherboard form factors – that is, the different sizes and specific or de-facto standards of major system components. In all cases, at least the motherboard footprint, mounting, and connectorization is specified. Less frequently, dimensions for cases and power supplies is also standardized. Power supply voltages and current requirements may also be given. The specifications are considered a form factor (as opposed to a model) when enough information is available so that FRU-level parts can be sourced from more than one OEM. There are actually many computer form factors. These can generally be classified according to category of application (especially in embedded systems) or by architecture (e.g. CHRP). However, this comparison is limited to ISA (IBM compatible) PC architectures, compatible evolutions of it (legacy-free), or form factors that have evolved to accommodate ISA-compatible CPUs (e.g. -ITX and ETX).