AMD chipset only with Xfire if using 2 or more ATI card not Nvidia
Nvidia chipset only with SLi if using GF cards only
cannot mixed it as it wont work, like I used M59SLI-S5 for AM2 that NF590 SLI that I can installed 2 of my 9600GT XXX and enabled into SLi, ok
If you look at other board like ASUS NF980 then you can use SLi with AM3 CPU