I have a old HP 3647h motherboard and on some website it says that it has 2 PCI x16 slots (which is true) but one of them is running at x4. One of the slots is black and the other one is white. How do i know which one is the one running at x4? (the website is http://www.findlaptopdriver.com/specs-hewlett-packard-3647h/)