The problem of switching between slots for SLI is usually dealt with through a mechanical SLI switch, but can be solved in a better way - and Gigabyte did. In the case of the 8N SLI Quad Royal, all important configurations can be enabled within the BIOS.
|PCIe Slot 4||PCIe Slot 3||PCIe Slot 2||PCIe Slot 1|
|inactive||3D1 card||3D1 card||x1|
As you can see, Gigabyte's 3D1 card is mentioned here as well. Here is how this works: Though basically being configurable in the BIOS, the 8N SLI Quad comes with an SLI paddle card or so-called SLI switch. While this usually determines whether an SLI capable motherboard runs all the 16 PCIe lanes into one x16 PCIe slot or splits them into two physical x16 slots running x8 mode, this paddle card has the sole function of enabling support for Gigabyte's dual GPU 3D1 SLI graphics cards.
Thanks to 16 PCIe lanes per nForce4 chip, two fully-featured x16 graphics clots can be powered. In that case, the two other x16 slots will work at x1 speed (as well the x1 slots, of course.)
Alternately, you can allocate eight PCIe lanes to each of the physical x16 slots, allowing you to run four bandwidth-consuming devices such as graphics cards.