Antilles Dual-BIOS Overclocking

The Radeon HD 6990 video card offers a special dual-BIOS feature that enables users to boot-up their computer with either a standard or factory-overclocked configuration. As the most powerful graphics card on the market there's more then enough performance available without the added GPU overclock, but some gamers and hardware enthusiasts may want to take a chance at setting a benchmark record or give their frame rate an extra boost. BIOS position '2' is the default shipping position, and yields 830 MHz GPU clocks at 1.12 volts each. BIOS position '1' is a hardware overdrive option, and increases the clocks to 880 MHz while adjusting voltage to 1.175 volts.

WARNING: AMD's product warranty does not cover damages caused by overclocking, even when overclocking is enabled via AMD software and/or the Dual-BIOS Function on the AMD Radeon HD 6990.

AMD and NVIDIA already stretch their GPUs pretty thin in terms of overclocking head room, but there's a difference between thin and non-existent. In this section, Benchmark Reviews compares stock versus overclocked video card performance on the Radeon HD 6990. Here are the test results:

GPU Overclocking Results

Overclocking Summary: Our baseline results show a 2.0~4.8% average increase in performance (at 1920x1200 resolution), which usually amounts to an added 2+ FPS in most games. That's not a whole lot of performance boost in relation to the increased power consumption, but every extra frame translates into an advantage over your enemy. In our overclocked testing with the Catalyst 11.4 'Preview' drivers, there were occasions when the driver would crash during a benchmark test, so it's unclear just how far enthusiasts can stretch the Radeon HD 6990. There were other issues to contend with, such as...

Radeon HD 6990 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 a modified version of FurMark's "Torture Test" to defeat NVIDIA's power monitoring and generate the maximum thermal load. This allows us to record absolute maximum GPU temperatures at high-power 3D mode. The ambient room temperature remained at a stable 20°C throughout testing. FurMark does two things extremely well: drives the thermal output of any graphics processor much higher than any 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 temperatures while gaming:

Although the Radeon HD 6990 uses an enhanced cooling solution with AMD's latest power efficiency technology, the temperatures did force the fan to run at audible levels most of the time. Resting at idle the Radeon HD 6990 measured 40°C in a 20°C room, which is actually on-par with some of the mid-range graphics cards. Once the GPU's were stressed to 100% using multi-GPU Furmark, the differences began to surface. The Radeon HD 6990 produced 84°C under full load (measured at 20°C ambient after ten minutes), which is similar to other video cards, but enough to force the cooling fan into a noisy high-power mode.

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