NVIDIA GeForce GTX 680 2GB Review

Author: SKYMTL
Date: March 21, 2012
Product Name: GeForce GTX 680 2GB
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New Overclocking Modes Explained

As we mentioned several dozen pages ago, the introduction of GPU Boost has led to some new challenges when trying to push clock speeds. Instead of dealing with the typical core, memory and shader clocks seen on current NVIDIA cards, the Shader domain clock has been eliminated since it runs at a 1:1 ratio with the rest of the processing engine.

There are also several other new options which allow users to increase performance like control over GPU Boost and the ability to modify power consumption for some additional overhead. The old fashioned way of overclocking has been thrown into the wind so properly harnessing every tool at your disposal will help maximize clocks and ultimately lead to optimal performance. For this section, we will be using EVGAís new Precision X tool but expect to see many of these same options make their way into MSIís AfterBurner, Gigabyteís SOC Tuner and ASUSí GPU Tweak utility in some form or another.

While Precisionís default interface changed to a drastic degree, its basic high level functionality has remained the same. It still allows you to overclock, monitor and generally tweak the hell out of your graphics card. We wonít drill down into every part of Precision X but there are three items youíll want to familiarize yourself with: Power Target, GPU Clock Offset and Mem Clock Offset. It is these sliders that allow clock speeds to be modified

To begin with, thereís one major caveat when overclocking a GTX 680: the Base Clock can never be increased. Instead, you will be using the offsets to achieve higher GPU Boost frequencies while modifying the minimum level at which GPU Boost will kick in.

At the reference speeds, Kepler will always strive to reach a certain power target by pushing clock speeds upwards via GPU Boost when the core isnít fully utilized, providing the preset operating range is adhered to. In order to begin overclocking it is always a good idea to set a higher Power Target so your clock speeds arenít artificially constrained by the default TDP limits. Just by moving this setting upwards without modifying anything else, increased performance can be realized since GPU Boost will be automatically given some extra headroom in some cases (but not all). Conversely, lowering the Power Target is an option for those of you who donít need to run at ultra high framerates and want to conserve electricity and lower heat output.

Playing around with the GPU and Memory Offsets is where the real fun begins. Remember that the default GPU Boost clock is 1058MHz and the vast majority of applications will likely cause the GPU to run at that speed. Bumping up the Offset literally heightens GPU Boostís range by the amount you set. For example, if you set an Offset of 125MHz, situations that saw the core running at 1058MHz will now cause it to Boost up to 1183MHz while games that allowed for 1150MHz would now strive for 1275MHz. The Memory Offsets behave in the same way except they arenít quite as constrained as the core is.

Of course, all of these numbers are dependent upon the card operating within its TDP limits. This is also why setting a Power Target is so important since without changing it, there would be much less headroom to play with. In addition, keeping the card cool will also ensure that it can run at higher GPU Boost clock speeds without slamming head first into a power and thermal barrier.

The last item we wanted to look at was EVGAís inclusion of a Framerate Target setting. With this enabled, the graphics card will try to attain a pre determined FPS without you having to enable VSync. Ultra high framerate situations increase power consumption and usually arenít beneficial to the end user so EVGA now allows for an artificial cap to be placed upon the card. This really is a novel idea which could (in the long run at least) decrease rendering inefficiencies in a way thatís invisible to the end user.

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