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.
The ATX pinout is really
a group of dual pin headers 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.
| Pin # | Signal Function | Pin # | Signal Function |
| 1 | +3.3VDC | 11 | +3.3VDC |
| 2 | +3.3VDC | 12 | -12VDC |
| 3 | COM | 13 | COM |
| 4 | +5VDC | 14 | PS_ON# |
| 5 | COM | 15 | COM |
| 6 | +5VDC | 16 | COM |
| 7 | COM | 17 | COM |
| 8 | PWR_OK | 18 | -5VDC |
| 9 | +5VSB | 19 | +5VDC |
| 10 | +12VDC | 20 | +5VDC |
Refer to ATX Main Power Connector Pinout for more information.
| Pin # | Signal Function | Pin # | Signal Function |
| 1 | COM | 3 | +12VDC |
| 2 | COM | 4 | +12VDC |
| Pin # | Signal Function |
| 1 | +12VDC |
| 2 | COM |
| 3 | COM |
| 4 | +12VDC |
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.
| Pin # | Signal Function |
| 1 | +5VDC |
| 2 | COM |
| 3 | COM |
| 4 | +12VDC |
The Auxiliary power header is used to power 5 volt or 3.3 volt peripheral components.
| Pin # | Signal Function |
| 1 | COM |
| 2 | COM |
| 3 | COM |
| 4 | +3.3VDC |
| 5 | +3.3VDC |
| 6 | +5VDC |
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.
| Pin # | Signal Function |
| 1 | GND |
| 2 | +12 volt |
| 3 | Sensor |
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.
| Pin # | Signal Function |
| 1 | +3.3VDC |
| 2 | +3.3VDC |
| 3 | +3.3VDC |
| 4 | COM |
| 5 | COM |
| 6 | COM |
| 7 | +5VDC |
| 8 | +5VDC |
| 9 | +5VDC |
| 10 | COM |
| 11 | COM |
| 12 | COM |
| 13 | +12VDC |
| 14 | +12VDC |
| 15 | +12VDC |
Memory Module formats and manufacturers are listed on the Memory Module Manufacturers page.
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, and use these tables only after checking the manufacturing sources of data.
Electronic Key words: ATX, Bus Standard, Interface Standard,
Specification, Spec, Interface, Physical Interface, Description, Personal
Computer Interface,
PC, Peripheral Interface, ATX Pinout, Pin out, Pins,
Pin Assignment, Signal Name, Header, Motherboard Pinout, Mother Board, Signal Assignment.
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