I've got an MSI GTX680 Lightning coupled with a lightly O.C'd 3770k and 16GB Crucial Ballistix @1600 on an MSI MPower Z77 board. (650 watt Thermaltake PS). I've read in COUNTLESS forums and posts that folks playing Far Cry 3, with a similar set up, are getting AWESOME frame rates at ultra or slightly less than ultra settings. Im at a little over High settings and getting around 20 fps, sometimes unplayable in certain areas. I've used the new Geforce optimizer, (Geforce Experience..), and this sets its to Very High settings optimally with the SSAO, Very High Post FX, and 2 times MSAA Anti Alliasing. Its UNPLAYABLE at this setting. Any one else having issues? And Im using the 314.07 drivers for my card. (Battlefield 3 runs at an AVG 90 fps maxed totally out GTW....its just this game!!) 1080p too!!
I have an MSI GTX 680 PE coupled with an older Core i7 860 with 16GB 1600mhz RAM (on Corsair HX650W) and I was running into similar issues, low/unstable frame rate and even crashes/blue screens. Turns out that my CPU was causing it since it was overclocked from stock 2.8 to 3.36ghz on stock voltage, I reset the BIOS, raised the base clock to 160 and no more issues. Far Cry 3 is very CPU demanding, task manager shows up to 85% usage on CPU in my case, check to make sure you didn't touch the voltages or accidentally mess up any other settings. Hopefully this was helpful. Good luck.
Hmmmm......I'm OC'd to 4.2 on stock voltage. I've had some random crashes also....Im gonna look into bumping that up. My Ivy runs pretty cool on a Hyper 212 Evo. I think I can handle a little more voltage. Right on!