that's an interesting question, you suppose to use the 2 slot I circle in white in dual SLI, but if you do so the back plate of the second GTX 580 will block the fan of the first GPU, the only way will be to use the slot in yellow for the second GPU , but I'm not sure of the speed of this one, they said x16 with the nf200 chip, someone have to confirm, Now doing so will make the card overhang the motherboard edge, so you will need a 8 slot case to hold it, and you may have problem with the connector under the GPU