Connecting a graphics card that has two connectors?

Hello guys, right now, i have a 2x 4850s. I'm thinking of upgrading to a 5850. What i'm wondering is, would i need to use two seperate cables with 6 pin connectors?
For example, my 4850s each have a 6 pin and 8 pin connector coming from one cable.
Ex: 1 4850 has the 6 pin connector connected to it and the 8 pin just sits around in the case
the 2nd 4850 has the 6 pin connector connected and the 8 pin connector is also just sitting in the case.
Would i need a cable with two 6 pin connectors to use a 5850? Or can i just use the 6 pin connector from the 1st cable and the 6 pin connector from the 2nd cable to power the 5850?
Sorry if this question is kind of confusing, this will be my first time doing an upgrade

my computer has an sli board, so the 2nd 4850 doesnt work x_x. It was a prebuild when i bought it.

Interesting. Who built that thing? haha.

You would just use the (2) 6 pins and plug them in the 5850. What PSU do you have? sounds pretty beefy if it has 2 6pin and 2 8pin.