Dell Precision T7500 SLI

Hi.

I have been trying so hard to get my two same brand GeForce GTX 680 cards to work in SLI mode on my Precision T7500.

I installed those cards on PCIe SLOT2 and SLOT4, and connected them through a standard SLI bridge from ASUS and MSI (I tried both but none of them works). I have also configured all BIOS options as default settings.

Both cards are recognized. The system boots. I can connect the HDMI cable to either card and it works. I can also see both cards on Windows Device Manager, and on nVidea Control Panel. However, I don't have any SLI settings there. I have run numerous tests and confirmed that SLI is in fact not working. I am using the latest 340 driver recently released from nVidia.

I know T7500 supports SLI, so this really frustrates me. Can you please help me out?