PSU Connectors & Certifications

PSU Connectors



Name & Description


Pinout & Colour codes



Main ATX Connector:

24pin (or 20+4) and older 20Pin

Main power connector.

Suitable for EPS / ATX boards.


The white -5Volt wire (pin 20) became obsolete with the removal of the ISA bus on modern boards. It is now missing on all 24pin connectors. See our PSU page for older PSUs with -5V wire.


Some Dell, WTX or AMD PSUs may have connectors with a different pinout.


Some HP Pavilion Slimline Computers require a PSU with a Mini 24pin

connector (37mm wide).

Ask for an adaptor.


Some wires, usually the orange wire at pin 13, may have a thinner brown wire attached to them. This is a sensor which monitors the voltage in the wire.

20pin: 43mm long

24pin: 51mm long



<<<< Note that an ATX  PSU with 24 pin can be plugged into a motherboard which has a 20pin socket. The 4 unused pins (black, red, yellow and orange wires) are simply left hanging. There is only one way the connector can be plugged in so there is no risk of error.

This may not be possible if some motherboard components are too closed to the socket and prevent the 24pin connector to be pushed all the way down. In this case ask for a 24 to 20 pin adaptor or cut the unused 4pin.



Molex drive connector:

4 Pin 5.25" drive connector for




Berg drive connector:

4 Pin 3.5" Connector for Floppy Drive and other peripherals.



SATA HDD Connector

Note that the orange +3.3V wire is not always present. SATA adaptors connected to a Molex do not include it. Most drives do not require this +3.3V wire.



3 Pin Fan Connector

(Obsolete. PSU fans are now controled

by the PSU itself rather than the motherboard)



8 Pin EPS connector: (Entry-level Power Supply) required on dual CPU boards.

On Big PSUs only.

May be supplied as 2x4pin connectors.




ATX 12V connector:

4 Pin connector for Pentium 4



Auxiliary ATX connector:

Sometimes required on old boards with AMD Dual CPUs to provide more power. Replaced in 2004 by the 24pin connector, this 6pin connector is now obsolete (the extra 3.3V and 5V rails it provided are now incorporated in the 24pin connector). See our PSU page for older PSU with Aux ATX Connector.

(Not to be mistaken for the P8 or P9 ATX connectors which look the same) 



PCI Express GFX connector:

6 Pin connector for PCI Express graphic cards. Mainly found on big PSUs.

Pin2 can be found empty, although the norm required a 12V yellow wire.



PCI Express connector:

8 Pin connector for PCI Express graphic cards. Can be an 8pin or 6+2pin connector. Mainly found on big PSUs.

Pins 6 and 8 Can be beveled or square. A beveled pin is universal and fits any socket. Pin2 can be found empty, although the norm required a 12V yellow wire.



AT P8 & P9 Connectors:

Only on old AT PSU.

P8 and P9 connector MUST be plugged in so that the black wires are side by side (together in the center)

(Not to be mistaken for the Auxilairy ATX connector which looks the same)

A similar looking P10 connector can also be found on some rare AT PSUs.

WIth 3x +3.3V orange wires or +5V red wires.




AT Switch:

Only on some old AT PSU

(Some AT PSU do not have it). 




Mini 6pin SATA power connector:

This tiny rare 10mm wide connector is used for slim optical drives.

Click here to see how to replace it.