"AMD has opened the CrossFireX architecture to Intel, allowing CrossFireX to be enabled on many Intel chipsets which feature two x16 PCI-E slots. SLI, however, requires a motherboard which is SLI certified, which includes all nForce chipsets (such as the nForce 590-SLi, nForce 680i-SLI, and nForce-790i), and most Intel X58 and Intel P55 based motherboards."
Source: Wikipedia