The ATX 4-pin power supply connector is a standard motherboard power connector used to provide +12 VDC to the processor voltage regulator.
ATX 4-pin 12V Power Connector Pinout (ATX v2.2)Wikimedia Commons
Below is the complete pinout table for the standard ATX 4-pin (2x2) 12V power connector as of Version 2.2 of the ATX Specification (PDF).
If you're using this pinout table to test power supply voltages, be aware that the voltages must be within ATX specified tolerances.
You can see other ATX power supply connector pinouts in our ATX Power Supply Pinout Tables list.Pinout Reference for ATX 4 pin 12V Power ConnectorsPinNameColorDescription1COMBlackGround2COMBlackGround3+12VDCYellow+12 VDC4+12VDCYellow+12 VDC2:23
How to Test the Power Supply in a Computer
The plug (male) is a Molex 39-01-2040 connector, the vertical receptacle (female) is a Molex 39-28-1043, and the right-angle receptacle is a Molex 39-29-1048.Pinout for the Standard ATX 24-pin 12V Motherboard Power Connector