So you probably have noticed that some motherboards have this little CPU power connector that's completely separate from the ATX connector. I've only seen these on brand specific mobos from Dell ...

I'm hardware-refreshing my old HTPC to an i5-3570K on a MSI Z77A-G41 which has an 8-pin 12V CPU power connector, and the PSU I have is an Antec Earthwatts EA-380 PSU, which has a 4-pin ATX 12V ...

Then connect the single power connector to the heat-sink fan power header on the motherboard. The Kühler H 2 O 620 only uses the CPU power connector.

A motherboard’s 8-pin power connector. It’s time to break out your favorite Phillips-head screwdriver and remove the screws holding the old motherboard to the mounting points in your PC’s case.

Corsair has also done the right thing with the four and eight-pin 12V CPU power connector by making it a 4+4-pin instead of having two separate ones that always leaves you with one cable too many ...

Two SATA cables with connectors at 50cm, 65cm and 80cm One 50cm 8-pin EPS 12V CPU power cable One EPS 12V CPU power cable with an 8-pin connector at 50cm and 4-pin at 65cm ...

Conceptually, it's a little like the supplemental power connectors that already feed power to the CPU socket.