Motherboard form factor

The term "form factor" is normally used to refer to the motherboard's geometry, dimensions, arrangement, and electrical requirements. In order to build motherboards which can be used in different brands of cases, a few standards have been developed:

• AT baby/AT full format is a format used in the earliest 386 and 486 PCs. This format was replaced by the ATX format, which shape allowed for better air circulation and made it easier to access the components;
• ATX: The ATX format is an upgrade to Baby-AT. It was intended to improve ease of use. The connection device on an ATX motherboard is designed to make plugging in peripherals as easy as possible (for example, the IDE connectors are located beside the disks.) What's more, motherboard components are arranged in parallel, so as to improve heat removal.
  • ATX standard: The ATX standard format is traditionally 305x244 mm. It includes an AGP connector and 6 PCI connectors.
  • micro-ATX: The microATX format is an upgrade to ATX, which has the same primary advantages in a smaller format (244x244 mm), with a lower cost. Micro-ATX includes an AGP connector and 3 PCI connectors.
  • Flex-ATX: FlexATX is an expansion of microATX which offers manufacturers greater flexibility when designing their computers. It includes an AGP connector and 2 PCI connectors.
  • mini-ATX: miniATX is a compact alternative to the format microATX (284x208 mm), and includes an AGP connector and 4 PCI connectors instead of 3 that come with microATX. It is mainly intended for mini-PCs (barebone computers).
• BTX: The BTX format (Balanced Technology eXtended), supported by Intel, is a format designed to improve upon the arrangement of components, so as to optimise air circulation, acoustics, and heat dissipation. The various connectors (memory slots, expansion slots) are aligned in parallel, in the direction in which air circulates. Additionally, the microprocessor is located in the front end of the case, by the air intake, where the air is freshest. The BTX power cord is the same as with ATX power supplies. The BTX standard defines three formats:
  • BTX standard, with standard dimensions of 325x267 mm;
  • micro-BTX, with small dimensions (264x267 mm);
  • pico-BTX, with much smaller dimensions (203x267 mm).
• ITX: The ITX format (Information Technology eXtended), supported by Via, is an extremely compact format designed for miniature configurations such as mini-PC. There are two major ITX formats:
  • mini-ITX, with small dimensions (170x170 mm) and a PCI slot;
  • nano-ITX, with extremely small dimensions (120x120 mm) and a miniPCI slot. For this reason, the choice of the motherboard (and its form factor) depends on which case is chosen. The table below summarises the characteristics of the various form factors.