"High performance" power mode = SLI. Unfortunately the default power setting is "balanced". That mode runs one video card until it detects an app requesting 3D graphics and then it switches to SLI.
I am building a new gaming machine this month, and in choosing a good motherboard I'm presented with PCI-e vs. SLI PCI-e boards. Lets say I'm going to spend ~$400 on my graphics card, or less if ...