AT motherboard Form factor is a measurement unit that defines the format and size (dimensions and configuration) of computer motherboards, enclosures, hard drives, interfaces, power supplies, and cards. A form factor defines the specifications of the case, power supplies, physical layout, and organization of the board. Form factors are available in various standards. AT (advanced technology) was the first form factor that gained popularity. IBM first presented it in 1984.

AT Design and Variants

The largest enhancement in AT over previous form factors was its tower design. It contains a front power switch. AT power supply offered three times more watts (192 watts) than older ones. The motherboard is 12 inches and does not fit in mini tower cases or desktops. AT form factor contains two 6-pin identical power connectors. Incorrect attachment of the connectors can cause damage. This is the reason of popularity of baby AT form factor. IBM launched it in 1985. Besides its small size it had almost the similar AT features. Now ATX and its variants have replaced it.

Balanced Technology Extended (BTX) Form factor

Intel proposed BTX (balanced Technology Extended) motherboard form factor in early 2005 to eliminate some of the problems with ATX motherboards. The major enhancements in BTX are its structural and thermal designs. Its backplane allows relatively easier integration of equipment. Also it is suitable for blade servers. Overall BTX layout design offers better hardware mounting points and cooling capabilities. Tower Case BTX motherboards can work with ATX power supplies.

Workstation Technology Extended (WTX) Form Factor

Intell launched WTX motherboard form factor in 1998. It is a larger form factor that can accommodate multiple processors and multiple hard disks to serve as a high-end workstation. WTX design offers high volume airflow through the chassis where the processors are placed. This provides better thermal management. The largest WTX motherboard size is 14 inch X 16.75 inch. So WTX motherboards offer more space to integrate additional components. WTX also contains specifications for WTX power supply unit. WTX chassis offers backward compatibility with ATX motherboard and so can contain ATX power supply.

Mini ITX Form Factor

Mini ITX is a small form factor and suitable for embedded systems. It mostly offers the same features as ATX, microATX, FlexATX, and BTX. The size of Mini ITX motherboard is 6.7 by 6.7 inches. Being low power consumption architecture Mini ITX motherboards are used in home theatres. Mini ITX form factor was launched by VIA Technologies in 2001. Now there are three standards of VIA's Mini ITX boards are available. First type of standards includes PL133 chipset boards, CLE266 chipset boards with MPEG-2 acceleration addition, and CN400 chipset boards with MPEG-4 addition. Second type includes EPIA M, MII, MS, CL, PD, and TC. Third type of standards includes EPIA SP series chipboards. All three standards use x86-compatible CPU.