Four pin as well as the 8 pin connector provide the same 12v power from the PSU to the CPU. Plug in the 4 pin and use. The extra 4 pins on the 8 pin are for better ground if using a more powerful, power draw CPU. Like a quad core for example.
thank you for answering, so it works , but i am usinga quite powerful CPU....
i5 2500k, will it be safe and stable ? Thanks !
You're referring to the 12v EPS power connector, which comes in 4-pin or 8-pin varieties. There are some that say that running 4-pin is unsafe and will damage the motherboard power stages (folks such as jaquith). I personally used my P8P67/2500k with only the 4-pin 12v EPS power connector. It worked like a charm.
I have since added in a 4-pin to 8-pin connector, primarily because my 4-pin connector barely reached the jack and using it as an extender was helpful. Here's a link: