So I have been running this GTX 680 in the middle PCIe slot on the Crosshair 2 formula for a couple of months now and its faultless - and is also bloody amazing!
Anyway, I was able to grab another identical GTX 680 and am attempting to run SLI. But am running into the same issue. As soon as I plug a single 680 into any slot other than the middle PCIe slot on the board - it has three - the system locks at the first post screen. I spoke with ASUS and they mentioned that they have seen this before and advised me to update the nForce drivers etc.
I didn't get anywhere after updating all my drivers. Bios, Chipset and latest Nvidia drivers. Essentially it looks like the ROG Crosshair 2 Formula will not run a 680 in any slot other than the middle white slot on the board. It is not capable of running SLI because that would mean inserting a card into a slot other than the middle one, which renders the system inoperable. This sucks, cos the system works awesome with THREE GTX 8800 OC2's installed. Its a great MOBO, and I hate having to pull a perfectly good setup, spend a whole bunch of money to update the board etc, when I have a feeling the answer is there somewhere. As stated above, I have a secondary system running here where the 680 works perfect in the primary PCIe slot, and its motherboard is a much lower spec one than the Crosshair 2.
Bottom line. It doesn't make sense that the Crosshair 2 Formula wont run the 680 in the primary PCIe slot. That's two different cards, that both work in the middle slot and/or another system. The cards are great, power is more than capable. Whats going on? Any more ideas? Or am I looking at having to drop hundreds of dollars to get another ASUS board that will run the way I want to?