To give you an idea as to how overclocking affects a Radeon HD 7950’s performance, we ran a handful of benchmarks on our card while it was configured a few different ways. First, we ran a set of benchmarks on the card 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 memory from 1250MHz to 1500MHz, and ran another set of tests. And finally, we retested the card with both its GPU and memory overclocked in concert.
Note that we performed all of the benchmark tests at a resolution of 1920 by 1200, with 4X MSAA enabled and all in-game graphical options set to their maximum values. We chose those relatively taxing settings to ensure that the graphics card--not another component, such as the CPU or RAM--was the performance bottleneck in our test system.
As you can see in the chart above, with the Radeon HD 7950, overclocking the GPU had a larger impact on performance than overclocking the memory did. Boosting the GPU frequency by 25 percent resulted in performance increases of 6.96 percent to 8.95 percent in the applications we ran. Increasing the memory frequency by 20 percent also yielded better performance, but the improvements were much smaller, falling in the 1.39 percent to 3.91 percent range.
Note, however, that memory-bandwidth-starved graphics cards would benefit more than the Radeon HD 7950 did from memory overclocking. A stock Radeon HD 7950 already offers upwards of 240 GBps of memory bandwidth--much more than most lower-end cards supply--so adding a few more gigabytes per second didn’t help much. That said, overclocking the GPU and memory simultaneously yielded performance increases much larger than the sum of the two overclocks: With both the GPU and memory overclocked, the Radeon HD 7950’s performance increased by at least 20 percent across our tests.
The proportionally larger performance increases that result from overclocking the GPU and memory concurrently are the result of the GPU being more fully utilized. Increasing memory bandwidth while simultaneously overclocking the GPU allows data to pass to and from the GPU more quickly, which results in better resource utilization and in turn increases performance.
Going the Extra Mile
While you can gain plenty of additional performance simply by moving a few sliders in your graphics card’s driver control panels, third-party utilities such as MSI’s Afterburner give users the ability to take overclocks even further by introducing voltage tweaks into the equation. Without performing any cooling modifications, however, we advise against altering your graphics card’s voltages. Increasing the voltages may allow for even higher overclocks, but doing so will also drive up heat output and power consumption significantly, over and above the increases resulting from the higher frequencies alone.