I do believe that has to do with the speed of the PCI express slot and it should at least support 16x but support older cards. Kinda confusing actually because if it has a pci express slot is it 8x or 16x mode? if it's saying "upto" my guess would be not higher. The HD4670 should work fine but check out that stupid marketing "upto" thingy. if any doubt steer clear of it. I like to make sure of my investment and if they can't get accurate info out about the product is there going to be that kind of same support?