6 pin MOLEX 39-30-1060 connector at the motherboard.
6 pin MOLEX 39-01-2060 connector at the cable.
The ATX optional power connector is a 6-pin Molex Mini-Fit Jr. auxiliary connector defined in early ATX12V power supply specifications. Unlike the main ATX power connectors, it does not carry primary supply rails; instead it routes ancillary signals — fan monitoring, fan speed control, a +3.3 V sense return, and FireWire (IEEE 1394) reference and voltage lines — between the power supply and the motherboard. It was specified for systems requiring close integration between PSU fan control and motherboard firmware, but was rarely implemented in practice and does not appear in later ATX12V or ATX 3.0 consolidated guides.
| Pin | Name | Color | Description |
|---|---|---|---|
| 1 | FanM | white | white |
| 2 | FanC | white | blue |
| 3 | 3.3V Sense | white | brown |
| 4 | 1394R | white | black |
| 5 | 1394V | white | red |
| 6 | Reserved |
Signals
- FanM — Fan monitor input; carries a tachometer signal from the PSU fan back to the motherboard for speed monitoring.
- FanC — Fan control output; allows the motherboard to send a PWM or voltage-based control signal to regulate PSU fan speed.
- 3.3V Sense — Remote sense return for the +3.3 V rail; allows the PSU to regulate voltage accurately at the point of load on the motherboard rather than at the PSU output.
- 1394R — IEEE 1394 (FireWire) reference signal; provides a voltage reference for the FireWire interface circuitry.
- 1394V — IEEE 1394 (FireWire) supply voltage line routed through the PSU connector harness.
- Reserved — Not connected; reserved for future use.
Notes
- The cable-side housing is Molex 39-01-2060 (Mini-Fit Jr., 6-circuit, dual-row, 4.20 mm pitch); the mating motherboard header is Molex 39-30-1060.
- Wire colours per the ATX12V specification: pin 1 FanM white, pin 2 FanC blue, pin 3 3.3 V Sense brown, pin 4 1394R black, pin 5 1394V red; pin 6 carries no wire. The colour column in the source table above reflects the original (corrupted) data in which all entries showed “white”; the correct colours are described here and in the Signals section above.
- This connector is distinct from the ATX auxiliary 6-pin power connector (Molex 90331-0010), which carries +3.3 V and +5 V supply current for high-load systems. They are not interchangeable.
- The optional power connector was present in ATX12V v1.x era specifications but was not carried forward into widespread adoption; most ATX12V v2.x and later power supplies omit it entirely.