AzureAbyss :
Just got my new mobo in and installed everything. But my 2 titans are not showing up in SLI configuration. They each work individually when i try them by themselves. but when i put them both in and put the SLI bridge on. it still only shows up as having one card. I'm beginning to think i may not have a big enough PSU.
my build is the mobo as stated in the title
2 evga gtx titans
32 gb 2400 ddr 3 ram
3930k processor
750 watt psu
A titan uses around 300 watts each, your CPU another 150 and you're out of power. Not to mention you should always overspec your powersupply as peak draw can jitter well above those numbers on any individual device, even if most of the time these parts use lower power than that.
Check your bios, check your SLi bridge (the strip on top of the cards connecting them).
Most graphics cards will represent their power state with a series of LED's and which would indicate if the cards aren't receiving enough power.
When you go to device manager can you see both cards? If you can but the nvidia properties don't let you enable SLi they could be underpowered. Or as above the Bios on your motherboard, or your SLi bridge needs investigating. If there is no second card in device manager, then again bios, reseat the video card, etc. If it's unknown, just reinstall the latest nvidia drivers.
Goodluck.