ATX motherboardATX stands for advanced technology eXtended. Intel introduced ATX form factor in 1995. Before ATX there was AT form factor for computer chassis and motherboards that had quite an overhead associated with it. ATX removed those overheads and became the default form factor for newer systems. With the board size of 305mm X 244mm (12-inch wide and 9.6 inch deep) ATX form factor allows its smaller standards such as microATX.

ATX Power Supply

The major advantage of ATX power supply is that software can switch on and off the computer power. That means there is no need to connect power supply directly to the power button. Often there is switch on the back of ATX power supplies to stop the power flow through the motherboard.

ATX Power Supply Connectors

ATX power supply connects to the motherboard through large keyed connector. This totally different from AT form factor where two connectors are used. This also allows the connection safer and easier. The voltage requirement for the connection is 3.3 volts. This means that there is no need for the motherboard to drive any voltage. Now in Pentium 4 an extra four-pin connector is used. This allows more power even for graphic cards.

ATX Power Supply Connector Standards

ATX power supply connector so far has gone through various standards. The first ATX connector was 20-pin. It supported Pentium III and Athlon XP. The next one was WTX 24 pin connector. It worked with Pentium II, III, Xeon, and Athlon MP. ATX12V was the next generation. EPS12V 24-pin connector consists of 8-pin secondary and 8-pin tertiary connectors.

Pentium 4 Connectors

Pentium 4 and Athlon 64 used this 20-pin connector. It was based on two parts. One is 8-pin tertiary and second is 4-pin secondary connector. It supported Xeon and Opteron. ATX12V 2.0 is the ATX power supply standard that contains 24-pin main connector with a 4-pin secondary connector. It allows PCI Express bus to work with Pentium 4 and Athlon 64.

ATX Motherboard's Power Requirements

An ATX motherboard in its typical configuration requires about 145 watts of power. For such configuration power supply must offer 720 mA current with +5 Voltage Stand By (+5VSB). In case a power supply does not provide such current some of the motherboard configurations will not work. Even there is a chance of power supply damage. Therefore it is a good practice to use always a certified power supply. For example with AMD processor always use AMD certified power supply. Moreover in case of heavy and configurations power supply requirements can vary.

ATX Chassis

ATX Chassis design removed the major drawback of onboard interfaces associated with AT design. Along with the keyboard and mouse the rear panel of ATX chassis provided onboard interfaces such as serial and parallel ports. This was not the case with AT Chassis design. The front panel was almost the same for general-purpose tasks (power on / off, Drives). Moreover panels were designed to support AT motherboards in ATX cases.