Motherboard

Also known as the mb, mainboard, mobo, mobd, backplane board, planar board, or system board. The Motherboard is a printed circuit that is the foundation of a computer and allows the CPU, RAM, and all other computer hardware components to function with each other. Below is a graphic illustration of the ASUS P5AD2-E motherboard and some basic explanations of each of the major portions of the motherboard. 

As computers advanced, so did motherboards; below is a listing of the various motherboard form factors and additional information about each of these form factors.

Full-AT
Baby-AT
LPX
Full-ATX
Mini-ATX
NLX

Full-AT (12" wide x 13.8" deep) Matches the original IBM AT motherboard design, which only fits into full size AT or tower cases only. This type of motherboard is not commonly found or used today.

• This form factor is no longer produced because it cannot be placed into the popular Baby-AT chassis.

Baby-AT (8.57" wide x 13.04" deep) Almost the same as the original IBM XT motherboard with modifications in the screw hole position to fit into AT style case, with connections built onto the motherboard to fit the holes in the case.

• Specific placement of the keyboard and the I/O slots.
• This board also cannot be placed into the slimline case.

LPX (9.00" wide x 13.00" deep) Developed by Western Digital when making motherboards, which was duplicated by many other manufacturers and is no longer made by Western Digital.

• The LPX motherboard riser card contains all of the expansion slots.
• Placement of the video, parallel, two serial and PS/2 connections have changed locations.

Full-ATX – (12" wide x 9.6" deep) / Mini-ATX – (11.2" wide x 8.2" deep) The official specifications were released by Intel in 1995 and was revised to version 2.01 in February 1997. The ATX form factor is an advancement over previous AT style motherboards. Therefore requires a new case design. ATX is not an abbreviation, it is actually a trademark which belongs to Intel.

• The ATX motherboard has a stacked I/O connector panel mounted on the motherboard.
• On a socket 7 ATX motherboard, the socket has been placed a further distance from the expansion slots, allowing for long boards to be placed in easier.
• Single keyed internal power supply connector. This is the Molex power connector, ATX 2.01. Standby voltage needs to be greater than 720 mA. The connector now cannot be placed in improperly. While the Molex power connector allows for 5v and 3.3v to be connected, it is recommended that only a 3.3v be connected to the motherboard.
• Relocation of the memory and the CPU creating better ventilation and easier upgrade.
• Power management possible with proper BIOS support.

NLX (Supports motherboards with overall dimensions of 9.0" x 13.6" [maximum] to 8.0" x 10.0" [minimum]) Implemented in 1998 by Intel and is similar to the LPX form factor; however, includes several new improvements.

• Support for the Pentium II
• Support for AGP
• Support for USB.
• Support for DIMM.
• Easier Access to internal components
• Support for motherboards that can be removed without using tools.

• Additional information and help can also be found on our Motherboard page.
• A listing of motherboard manufacturers can be found on our motherboard links page.

Also see: Backplane, Form factor, Motherboard definitions, Northbridge, Southbridge, Standout