Stepping your graphics card's GPU beyond its specified clock speed will improve its performance and may stave off an expensive upgrade. We'll show you how to do it safely.
MANY PC GAMERS eagerly await the release of next generation graphics boards, hoping that the new hardware will boost frame rates and make the latest games look better. But while such upgrades usually do increase game performance, improve image quality, or both, high end boards are expensive and may not be necessary.
Today, even midrange graphics cards are generally fast enough to pump out buttery smooth frame rates in cutting edge games at all but the highest resolutions. If your current graphics card is serving you well, and you just want a little something extra to pep up performance, overclocking may be the better way to go. It will certainly be more affordable.
Why Overclock?
In its early days, overclocking may have been a black art reserved for hard core computer geeks, but today it's about as easy as can be, and it's usually safe too. Yes, overclocking a component can shorten its life span. But if you don't push things too far. and if you keep temperatures under control, you have little reason to worry.
One key is to ensure that your PC has an adequate cooling system and a power supply that can handle an overclocked board. Modern graphics boards have thermally controlled fans that spin faster to dissipate heat from an overclocked board. The card may be a bit noisy as a result, but if the overclock remains stable and the graphics card's cooler keeps up, you should be good to go.
Both AMD and Nvidia (thebig two graphics board makers) have built overclocking tools into their drivers. AMD's are readily available (on supported boards) in the AMD Overdrive tab. listed in the company's Catalyst Control Center software suite (in the Performance section). Nvidia's overclocking tools aren’t exposed by default in its GeForce drivers, but installing its System Tools utility will make them available. Simply pick up and install the Systems Tools utility from Nvidia.com; frequency controls will then be visible in the performance and tuning section of the GeForce driver.
Disregarding software/driver optimizations, game engine tweaks, and system interface speeds, the performance of a graphics board is typically determined in part by the computing speed and fill rate of its graphics processing unit (GPU), and in part by the amount of memory bandwidth its frame buffer memory affords. (The amount of frame buffer memory on the card can also come into play as resolutions and texture sizes increase, but we don’t have space here to discuss those factors in depth.) By increasing the frequencies of the GPU and the frame buffer memory on your graphics board, you can make them process and move more data, more quickly, increasing overall performance.
How to Overclock
Overclocking a graphics board is a fairly straightforward process. All you need is a working and properly configured graphics board, and a few of your favorite games or a benchmark like Futuremark 3DMark 11 to test stability. For the purposes of this article, we used a brand-new AMD Radeon HD 7950 installed in a high end. Intel powered test gaming system running Windows 7 Ultimate (64-bit).
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| AMD RADEON HD 7950 card improved its frame rate on Lost Planet 2 by 20.48 percent after overclocking. |
Before you begin overclocking, install the latest drivers for your graphics board (and Nvidia's System Tools if necessary), and play a few games to ensure that the system is stable. If all is working well, restart the system, open the graphics board's control panel, and navigate to the overclocking or frequency control section; we used the Overdrive tab built into AMD’s drivers.
First, enable Overdrive by ticking the necessary box, and max out the power control settings to eliminate any power related frequency restrictions. Next, increase the GPU frequency by moving the appropriate slider by a few megahertz at a time, and apply the settings. Then play a game or loop a benchmark to test stability.
For example, our Radeon HD 7950*s GPU was clocked at 800MHz by default. We started by moving the GPU clock settings slider in increments of 10MHz, until our test system became unstable. As soon as we encountered any visual anomalies, or a game or the system crashed, we turned the GPU frequency back down by 10MHz and tested for stability again. Ultimately we settled on a stable GPU frequency of 1000MHz — a 200MHz increase over stock.
Once we had determined our peak GPU frequency by using the method just described, we set it back to its default clock speed and then focused on the graphics card's memory. By default, the Radeon HD 7950’s memory is clocked at 1250MHz. We used the same procedure of increasing the memory frequency by 10MHz increments, and testing the board's stability at each step of the way. In the end we achieved a stable memory frequency of 1500MHz.
We recommend overclocking the GPU and the memory separately to isolate any instability that the tweaking may introduce to that particular component. Once you know the peak frequency for both, set the GPU and memory to those speeds simultaneously and test for stability once more. If all is well, you're done. If not. lower the frequencies a bit more, and retest the graphics card. Some graphics boards may remain stable while overclocked, but offer lower performance when running at higher frequencies due to thermal or power throttling. If your system behaves that way, reduce the GPU and memory frequencies until performance begins to scale properly.
The Results
To see how overclocking affects a Radeon HD 7950’s performance, we ran a handful of benchmarks on our board while it was configured in different ways. First, we ran a set of benchmarks on the board while it was in its stock configuration. Then, we overclocked the GPU from 800MHz to 1000MHz and ran a second set of numbers. Next, we overclocked only the card’s memory, from 1250MHz to 1500MHz. and ran another set of tests. And finally, we retested the board with both its GPU and memory overclocked in concert.
Overclocking the GPU and memory together yielded performance gains much larger than the sum of the two overclocks taken separately: Performance rose by at least 20 percent.
We performed all of the benchmark tests at a resolution of 1920 by 1200. with 4X MSAA enabled and all ingame graphical options set to their maximum values. We chose those relatively taxing settings to ensure that the graphics board — and not another component, such as the CPU or RAM — was the performance bottleneck in our test system.
As the chart above shows, with the Radeon HD 7950, overclocking the GPU had more impact on performance than overclocking the memory did. In the applications we ran. boosting the GPU frequency by 25 percent led to performance increases of 6.96 percent to 8.95 percent. Increasing the memory frequency by 20 percent also yielded better performance, but the improvements fell in a more modest range of 1.39 percent to 3.91 percent.
Memory bandwidth hungry graphics boards would benefit more than the Radeon HD 7950 did from memory overclocking. A stock Radeon HD 7950 offers upward of 240 gbps of memory bandwidth - much more than most lower end boards can supply — so adding a few gigabytes per second didn’t help much. Still, overclocking the GPU and memory together yielded performance gains much larger than the sum of the two overclocks taken separately: With both GPU and memory overclocked, the Radeon HD 7950's performance rose by at least 20 percent across our tests.
The proportionally larger performance increases that result from overclocking the graphics processor and memory concurrently are the result of the GPU's being more fully utilized. Increasing memory bandwidth while overclocking the GPU allows data to pass to and from the GPU more quickly, yielding better resource utilization.
Going the Extra Mile
You can gain plenty of extra performance by moving a few sliders in your graphics card's driver control panels, but a third-party utility such as MSI's Afterburner lets you take overclocking further by introducing voltage tweaks into the equation. Unless you perform cooling modifications, however. we advise against altering your graphics board's voltages. Increasing the voltages may allow for even higher overclocking, but doing so will also drive up heat output and power consumption significantly, over and above the increases that are due to higher frequencies alone.
How Much Does Overclocking Help Performance?
| Game | Stock Radeon HD 7950 | GPU overclocked to 1000MHz | Memory overclocked to 1500MHz | GPU & memory overclocked | ||||||
| Performance | Improvment over stock | Performance | Improvment over stock | Performance | Improvment over stock | |||||
| Alien vs. Predator (frame rate) | 46 fps | 49.2 fps | 6.96% | 47.8 fps | 3.91% | 55.2 fps | 20% | |||
| Far Cry 2 (frame rate) | 103.82 fps | 112.62 fps | 8.37% | 106.26 fps | 2.25% | 124.83 fps | 20.17% | |||
| Lost Planet 2 (frame rate) | 50.3 fps | 54.8 fps | 835% | 51 fps | 1.38% | 60.6 fps | 20.48% | |||
| Unigine Heaven 2.5 | (frame rate) | 35.3 fps | 38.4 fps | 8.78% | 36.1 fps | 2.27% | 42.5 fps | 20.4% | ||
| (benchmark score) | 890 | 967 | 8.65% | 910 | 2.25% | 1071 | 20.34% | |||
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