In our original preview we really covered everything above. With that said, we couldn't talk about the PCIe x16 slots and what they run at. Now we can and looking above, you can see we've got support for a three card setup along the four PCIe x16 slots.
If you're going for two cards, you'll use the two blue PCIe x16 slots and they will both run at x16. If you throw a third card into the mix and use the first white PCIe x16 slot then the setup will move to a x16 / x8 / x16 one.