"The other day the new GIGABYTE P45-DQ6 arrived and I was instantly intrigued by how cool it looks. The thing is, what also arrived that day was the HD 4850s. With my mind going in over drive, I thought this was the perfect time to check out what’s going on in the PCI Express slot department these days.
While there are a few differences between the two, we only cared about one of them. We wanted to know the performance difference between the X48 and the P45 when running Crossfire. While both boards carry two physical x16 slots, when two cards are installed the electronics behind the slots on the P45 tune back to x8 on both slots. The X48 on the other hand continues to run both slots at x16 independently."