After doing some research on the
difference between the 680i and the 680i LT.
The difference between between these 2 boards is
the 680i uses the 590MCP where as the 680i LT uses the 570MCP.
The 590MCP lets you run 2 cards at full x16 speed.
The 570MCP will reduce the speed down to x8 if your running SLI.
And since your 7950 GX2 is a dual gpu card, maybe that's why it's running at x8
instead of x16.forum topic #1forum topic #2