If you plan on purchasing a 1440p monitor and want it to operate at higher than 82hz, please DO NOT buy an Nvidia video card. Nvidia started off as the best card for overclocking and many of us (including myself) purchased the Kepler series of cards. The Kepler (GTX 6xx) series were the first cards capable of pixel clock operating beyond 400mhz, which would get you up to 135hz refresh rate on a 1440p monitor. The previous Nvidia cards would work up until 400mhz, or around a 102mhz refresh rate on a 1440p monitor. This is all while using an SLI setup was limited to 400mhz as well, whether you're using Kepler or not. So...let's just point form what I said:
Kepler Series Cards (Single Card): 120hz+ (537mhz+ pixel clock limit)
Kepler Series Cards (SLI): 102hz (400mhz pixel clock limit)
Older Nvidia Cards (Single or SLI): 102hz (400mhz pixel clock limit)
As of 2 months ago, we noticed Nvidia beta drivers were acting oddly, and restricting the pixel clock to 330mhz. Any attempt to set a custom resolution through the Nvidia Control Panel would just give an error saying it's not supported by your device. It wouldn't attempt to do it and fail. It just popped up with an error. And previously added custom resolutions that were visible, would not load. We created a thread on their forums, and brought attention to it. We received no responses, and subsequently their forums were hacked and have been offline for 2 months now. One of the responses we had received through one of Nvidia's channels was that the limitation was due to a security feature built into their beta drivers, and that it is not indicative of what will be going into the live drivers.
I wish that had been true. During that time we tried out 2 consumer beta, and 1 developer beta driver. All had the same limitation. And what finally sealed it...with the launch of the GTX 660ti card, the latest non-beta WHQL certified driver for the card, has a strict across the board limit of 330mhz pixel clock. If you remember from the launch of the GTX 690 and GTX 670, the drivers available at launch for those cards were released as the standard drivers for the entire Kepler range of cards within 1-2 weeks. So all Kepler cards will soon be hit with this 330mhz pixel clock limit. What does this mean for us now? Well...let's recap as I did earlier:
Kepler Series Cards (Single Card): 82-84hz (330mhz pixel clock limit)
Kepler Series Cards (SLI): 82-84hz (330mhz pixel clock limit)
Older Nvidia Cards (Single or SLI): 82-84hz (330mhz pixel clock limit)
What does this mean for you? Well, currently the best option is to purchase AMD video cards. There is a driver mod for AMD video cards that allows an unlocked pixel clock for both Single Card and Crossfire setups (though some have reported certain limitations with Crossfire still). You can follow ToastyX's thread by clicking here.
To make it more clear, this is where Nvidia and AMD stand at the moment (or rather, will in a few weeks):
Nvidia Cards: 82-84hz (330mhz pixel clock limit)
AMD Video Cards: 120hz (theoretically 600mhz+ pixel clock limit)
We are certainly upset that instead of moving forward, Nvidia has decided to remove functionality that was the main reason many of our current and future members purchased their cards. Stealing functionality, while legal from their end, is a terrible idea from a consumer standpoint and we strongly disagree with it. But all we can do is advise you of these changes and continue our attempts to contact Nvidia to see if they'd be willing to reverse this decision.