Is this what you are referring to?  6 pin P4 connector.  These old psu in PATA/ide era had no sata connector. The 6 pin connector can be connected to an adapter to make a sata power connector. P4 has yellow, red, orange wires for 12/5/3.3V.  The 5 wires you saw correlate to intended sata purpose. [IMAGE]   [IMAGE]  
like the title says what uses the 6 pin connector that has 12v, 5v, 3.3v, gnd, gnd, and nc?all I see is people listing the pinout or a way to CREATE not USE this connector (ie it allows a standard atx sta to simulate this connector not actually connect to it)this connector has been around for decades yet I never see a device that takes it
what is the USE for the 6 pin proprietary psu connector