Learning Objectives

3. AT motherboard (about 12×13 inches in size) was followed by the Baby AT (about 8.5×13 inches in size).

4. A number of different form factors appeared and quickly disappeared, including the Slimline LPX (sometimes referred to as Low-Profile Extensions) and the NLX.

a) The LPX features a case height of about 4 inches and has a limited number of expansion slots mounted on a central riser card.

b) The LPX, also small, provides better support for CPUs, AGP video, USB, and large amounts of RAM.

NLX: New Low Profile eXtended
LPX: Low Profile eXtension

How Motherboards Work

• 6. The ATX form factor
• a) In 1995, Intel introduced a new form factor called ATX. Roughly the same size as the Baby AT, it mounted at a 90-degree angle relative to the computer’s case. It featured a rear panel with all necessary ports built in. It had a mini-DIN or PS/2 keyboard and mouse port. The position of the power supply allowed for better cooling. The CPU and RAM were more accessible.
• b) RAM was closer to the Northbridge and the CPU than on AT boards, allowing the clock speed to be doubled or quadrupled.
• c) It incorporates “soft power” features, allowing the operating system software to turn the PC on and off. Instead of a large power cord from the power supply to the on/off switch, the ATX board runs the power through the motherboard itself and uses only a pair of small wires from the motherboard to the on/off switch.
• d) It has only a single 20-pin connector, called P1, from the power supply to the motherboard.
• e) A number of variations of the ATX have been produced, including the microATX and the FlexATX.

How Motherboards Work

7. BTX form factor designed to be cooler than other boards.

a) BTX designed to replace ATX

b) MicroBTX designed to replace microATX

c) PicoBTX designed to replace FlexATX

8. Some manufacturers produced proprietary motherboards.