|VisionTek 900338 Radeon HD 6870 Video Card|
|Reviews - Featured Reviews: Video Cards|
|Written by Olin Coles|
|Saturday, 30 October 2010|
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AMD Barts GPU Overclocking
AMD's Cypress GPU was well-known for accepting massively overclocked speeds. The new Barts GPU is based on Cypress, and should in theory yield a similar overclock. This presumes that AMD hasn't already stretched the Radeon HD 6850 and 6870 as far as they could go. For this project, we used MSI's free Afterburner program to overclock the video cards.
The MSI Afterburner "Graphics Card Performance Booster" application offers several adjustable variables to reach the desired overclock. Afterburner allows for voltage changes (increase/decrease), but this project aimed to stretch the AMD Barts GPU as far as it could go without any extra power applied. Beginning with the maximum stable GPU clock speed, I slowly increased the settings until I began to see tearing or the driver crashed. Once I reached the most stable speeds for both GPU and GDDR5, I put the video card back into action with high-demand video games for additional benchmark tests. Here are the results:
AMD Radeon HD 6850 Overclocking Results
AMD Radeon HD 6870 Overclocking Results
Radeon HD 6870 Temperatures
Benchmark tests are always nice, so long as you care about comparing one product to another. But when you're an overclocker, gamer, or merely a PC hardware enthusiast who likes to tweak things on occasion, there's no substitute for good information. Benchmark Reviews has a very popular guide written on Overclocking Video Cards, which gives detailed instruction on how to tweak a graphics cards for better performance. Of course, not every video card has overclocking head room. Some products run so hot that they can't suffer any higher temperatures than they already do. This is why we measure the operating temperature of the video card products we test.
To begin my testing, I use GPU-Z to measure the temperature at idle as reported by the GPU. Next I use FurMark's "Torture Test" to generate maximum thermal load and record GPU temperatures at high-power 3D mode. The ambient room temperature remained at a stable 20°C throughout testing, while the inner-case temperature hovered around 37°C.
FurMark does two things extremely well: drive the thermal output of any graphics processor higher than applications of video games realistically could, and it does so with consistency every time. Furmark works great for testing the stability of a GPU as the temperature rises to the highest possible output. The temperatures discussed below are absolute maximum values, and not representative of real-world performance.