The ATX: MotherBoard format is 12" wide x 9.6" deep (305mm x 244mm).
The ATX mother board is essentially a Baby AT mother board rotated 90 degrees in the chassis.
The board was rotated in the Chassis to allow for improved air flow.
Power Supplies will indicate the standard which they comply to, in this case the notation ATX12V indicates the power supply compiles with these pinout tables.
Pin out tables for ATX connectors are listed below. Note the power supply does have to comply with ATX12V for the connectors to match.
The ATX pinout is really a group of dual or single-row pin headers [with latches] located on the Mother board.

Refer to this page for the pinout for the EmbATX motherboard header pinout or BTX motherboard header pinout.
Additional Mother Board form factors and processor types are listed on the OEM MotherBoard Manufacturers page.

Header Pin-Outs for the ATX Mother-Board are shown below. Each is defined as a Molex connector, or its equivalent.

Refer to ATX Main Power Connector Pinout for more information.

The power connector pinout for the Floppy drive on an ATX mother Board is shown below.
The motherboard may not use a four pin header to supply power to the FDD,
in which case one of the molex cables from the power supply needs to be used.
Refer to the Floppy Drive Power Connection for additional information.
The ATX12 specification still defines a floppy power cable.

The Auxiliary power header is used to power 5 volt or 3.3 volt peripheral components.

One version of the ATX power connector for the Fan is shown below.
The third sensor pin is relatively new and allows the mother board to adjust the fan speed as the case/IC temperature changes.
Pin 3 may not always be available, but the table provides the ATX pinout.
Refer to the ATX Fan Control page for other possible variations.

The power connector for the Serial ATA drive is shown below.
The Serial ATA [SATA] Hard Disk Drive [HDD] is the new standard for Hard disk drives, using a serial interface;
[instead of the large parallel flat ribbon cable of the past].
This is the ATX pinout for SATA power, refer to the SATA page for the signal pin out.

Memory Module formats and manufacturers are listed on the Memory Module Manufacturers page.

Computers Manufacturers list, or use the Equipment icon below.

A few computer manufacturers may use non-standard or proprietary components in their systems to reduce costs.
The pinout for the power headers listed on this page comply with the ATX specification.
However some companies may use pinouts that differ from the pin out tables above.
First try to determine the pin out of the headers listed above from the manual that shipped with the computer.
Use these tables only after checking the manufacturing sources of data.

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