OK, when using say a 750W power supply with a single 12V rail using a 8 pin to 2x(6+2) splitter is OK. No need to connect up another 8 pin PCI-E cable.
My reasoning is that since the power supply in question is a single rail 12V, it does not matter.
Also, the spec for PCI-E 6 pin is 75W and 8 pi is 150W. Since the connector is coming from an 8 pin port on the power supply, the 6 pin should be able to indeed supply 150W as well, the only difference is the 2 additional ground wires.
My reasoning is that since the power supply in question is a single rail 12V, it does not matter.
Also, the spec for PCI-E 6 pin is 75W and 8 pi is 150W. Since the connector is coming from an 8 pin port on the power supply, the 6 pin should be able to indeed supply 150W as well, the only difference is the 2 additional ground wires.