4 pin MOLEX 39-29-9042 connector at the motherboard.
4 pin MOLEX 39-01-2040 connector at the cable.
The ATX12V +12 V power connector is a dedicated 4-pin Molex Mini-Fit Jr. (4.20 mm pitch) connector introduced with ATX12V version 1.0 in 2000 to supply additional +12 V current to the Pentium 4 CPU voltage regulator module. It is defined in the Intel ATX12V Power Supply Design Guide and is used identically on both ATX and BTX platform motherboards. Two pins carry ground and two carry +12 V, with a maximum current rating of 8 A per circuit. It is often called the P4 connector or CPU12V connector, and many later power supplies ship a 4+4 split cable that is also compatible with the 8-pin EPS12V socket.
| Pin | Name | Color | Description |
|---|---|---|---|
| 1 | COM | black | Ground |
| 2 | COM | black | Ground |
| 3 | +12VDC | yellow | +12 VDC |
| 4 | +12VDC | yellow | +12 VDC |
Signals
- COM — Ground return; both pins 1 and 2 carry ground (black wire, 18 AWG).
- +12VDC — +12 V supply to the CPU voltage regulator module; both pins 3 and 4 carry +12 V (yellow wire, 18 AWG). Voltage tolerance is ±5% (11.40–12.60 V).
Notes
The connector uses Molex Mini-Fit Jr. dual-row housings with a polarisation tab that prevents orientation reversal. The cable-side receptacle is Molex 39-01-2040 and the correct mating board-side header is Molex 39-29-9042 (vertical through-hole receptacle), as specified in the ATX12V v1.3 Design Guide. The Molex 39-28-1043 number refers to the right-angle board variant of the same connector family and may appear in some motherboard documentation, but 39-29-9042 is the primary mating part called out in the Intel specification. Note that the physical housings of the ATX12V 4-pin and EPS12V 8-pin connectors are of the same Molex family and can sometimes be mechanically forced into a wrongly-polarised socket — always verify orientation before applying power.
Connector part numbers
- Motherboard connector: Molex 39-29-9042 (vertical; also listed as 39-28-1043 right-angle variant)
- Cable connector: Molex 39-01-2040
- Terminals: Molex 39-00-0168, Molex 44476-1111
- Maximum current per circuit: 8 amps