Actually I believe the 6-pin is two +12V, three ground, and one null, and the 8-pin is three +12V and five ground.
Of course there's nothing stopping you from taking the 8-pin head off and putting the relevant wires into the 6-pin... Just don't screw up or your graphics card might fry.
Of course there's nothing stopping you from taking the 8-pin head off and putting the relevant wires into the 6-pin... Just don't screw up or your graphics card might fry.