While X79/SNB-E is a native Gen2 platform, some motherboard manufacturers have enabled Gen3 speeds. With our GTX 680 launch drivers, we will only be supporting Gen2 speeds on X79/SNB-E while we work on validating X79/SNB-E at these faster speeds. Native Gen3 chipsets (like Ivy Bridge) will still run at full Gen3 speeds with our launch drivers.
GeForce GTX 680 supports PCI Express 3.0. It operates properly within the SIG PCI Express Specification and has been validated on multiple upcoming PCI Express 3.0 platforms. Some motherboard manufacturers have released updated SBIOS to enable the Intel X79/SNB-E PCI Express 2.0 platform to run at up to 8GT/s bus speeds. NVIDIA is currently working to validate X79/SNB-E with GTX 680 at these speeds with the goal of enabling 8GT/s via a future software update. Until this validation is complete, the GTX 680 will operate at PCIE 2.0 speeds on X79/SNB-E-based motherboards with the latest web drivers.