Thursday, May 2, 2013

Pixel Clock overclocking without a GeForce Titan?

NVidia’s GeForce Titan brought the single GPU performance to a new level. So did the single GPU price. But they were not the only things it brought to the table. There were some fancy features, and one of them was Pixel Clock Overclocking.

We all know that most displays these days run at a native resolution of 60Hz. While 60Hz is enough for most things, you can actually get some benefit out of displays running at a refresh rate higher than 60Hz in some specific use cases. One such use case is gaming. If you have a graphics card with enough juice to give more than 60FPS, your frame animations will be more fluid on a display that runs at a higher refresh rate.

120Hz displays are becoming more and more common place – among gamers at least – because of this reason. I haven’t actually used a 120Hz display, but most people speak so highly of the improvement after the upgrade. Sure, you need a GPU capable of pushing those frames past 60FPS to get any advantage. These displays were primarily made for 3D because the actual refresh rate halves when you use 3D. But you don't have to use 3D to get the benefits of a 120Hz display.

By overclocking your display’s Pixel Clock, you can raise the refresh rate beyond the stock refresh rate. This not only applies to 60Hz displays, but 120Hz displays as well. Just with standard CPU and GPU overclocking, how much you can increase the refresh depends on luck. You won’t get the same results between two identical displays. You have to find out what your display is capable of, on your own.

While Pixel Clock Overclocking is a feature that’s officially supported only on the Titan, you can use EVGA’s PrecisionX utility to enable it with any GeForce 600 series graphics card.

Here's how you do it.

PrecisionX Main Window


PrecisionX Settings Page (first tab)


Pixel Clock OC settings


I have a NVidia GeForce GTX 670 2GB made by Palit and a Iiyama ProLite E2773HDS display which runs at 60Hz. I was able to raise the refresh rate of the display to 69Hz. Anything beyond that would make the video kind of vibrate. Check out the following video to see what happens when you go beyond the capabilities of the display. Just to be safe, when you are overclocking the Pixel Clock, do it one Hz at a time and as soon as you find out any anomalies, jump back to the previous stable refresh rate.


Pixel Clock Overclocking - what happens when you go beyond the limits

Also note that once you select and apply an overclocked refresh rate, it is reflected in the NVidia control panel. And the setting will retain when you reboot Windows. You don't even have to run PrecisionX again. But if you want to revert or change the setting, you will have to do it via PrecisionX utility the same way.

So, what kind of impact does it have on the gameplay? Well, 60Hz to 69Hz isn't a big leap. I cannot really say if it is smooth or not. It should be, and that's enough. Perhaps, to see a notable difference, you really want a true 120Hz display. I know what my next upgrade could be: a 120Hz display for gaming and run dual monitors with the one I have. I wonder if I can run them at difference refresh rates though. I don't think a 27" 120Hz would be cheap either.

One thing I noticed after the display overclock was that the monitor not takes more time to resume from standby. The Iiyama Prolite E2773HDS is very slow in this respect even at stock. (It takes about 5 seconds to resume from standby) Out of all the displays I've used, this is the slowest.

Edit: I just checked the prices of 27" 120Hz displays and the Iiyama ProLite G2773-HS is available for just ¥26,800 on Amazon. That's not too bad, is it?

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