SLI Compatibility

I have two Nvidia GTX 580 cards and even tho MSI Afterburner tells me both cards are used at 70% only one card actually warms up.
If SLI compatibility is already implemented, is it done using a central load balancer or are fixed threads spawned?

I’ve got my quad 7970 setup unbalanced, i get only the first 2 cards loaded so i don’t think there’s multi card compatibility

Crossfire should work, as to the game it just appears like one card. SLI will only use one card.