bcavnaugh
Look on page 1-24 in your manual.
They recommend a single Card on this motherboard as well.
Is your PSU big enough to support 2 GTX 780s? What is the Size or Make and Model?
Is your on board video on or off?
What did ASUS say about this issue?
One last item can you see two cards in the BIOS?
I have never seen a setting in the Bios to set SLI in any of my ASUS or EVGA Motherboards.
Bill
That's not what the manual says. Instead, the chart shows that if you are using a single video card, the preference is to use the first 16x slot, and not the second. If you are using 2 video cards, then you use the first and second 16x slots, of which both will run at 8x.
The board appears to support SLI. As noted, there shouldn't be anything in the BIOS needed to be changed for SLI. Some boards require jumpers to be changed for SLI/CFX, but this isn't one of them. Just make sure you have the cards in the first two 16x slots, and not the one at the bottom of the board.
If there are BIOS settings that need to be changed, go into the BIOS > Advanced Mode > System Agent > Graphics Configuration. Make sure that the primary display is set to PCIE, and the Multi-Monitor setting is Disabled.
Make sure your chipset drivers are installed first. If you've already installed the chipset drivers, then try installing the graphics drivers with the SLI bridge
off, and use the Custom Install, with the Perform a Clean Install option checked. Make sure both cards are seen in Windows Device Manager. Assuming they are, shut the system off and replace the bridge, boot back up and see if the option to enable SLI is available.
If SLI is still not available, try posting the rest of your system specs here. Also, test the cards individually, to make sure both cards POST, and give picture. At the very least, make sure to reseat both cards, in case one is not making good contact. If one of the cards is not operating properly, that could be the reason you're having issues. Also, do not manually set the GPU you want for PhysX in the Nvidia Control Panel; just leave it on auto. Finally, if using multiple monitors, make sure you have all the monitors are on the primary card, unless you are using Surround.