The Sapphire HD7870 OC Edition 2GB DDR5 graphics card comes with effective base clock speed of 1050MHz and the memory set to run at 1250MHz. This is a small factory overclock compared to the reference Radeon HD 7870 design of 1GHz core and 1200MHz memory. The overall increase of 50MHz on the GPU's operating speed and 50MHz increase on the memory should provide improved performance Out-of-Box without the user having to change anything.
To overclock the Sapphire HD7870 OC graphics card we are using Sapphire's overclocking utility TriXX. We found the highest GPU core clock without voltage tweaking at 1245MHz. Compared to its Out-of-Box settings this is an increase of 195MHz and 18.6% faster operating frequency. Next we found the highest memory clock which was 1560Mhz. Compared to the stock Sapphire HD7870 OC this is an increase of 310MHz and 24.8% faster operating speed. We increased the slider by 82mV up to 1.3V. The voltage increase allowed an additional 25MHz bringing the highest stable overclock to 1270MHz. The overall speed increase from the overclock on the GPU is 21% faster compared to the Out-of-Box operating speed.
The 7000 series AMD video cards provide better performance than its last generation competition while also being more power efficient. The extra power consumption that the overclock required was still more power efficient than the Radeon HD6970 and GeForce GTX570 with a marginal performance advantage.
Under full load the temperature of the Sapphire HD7870 OC graphics card increased by 37C up to 61 degrees Celsius with fan speeds only reaching 45%. The fans were not audible over the normal operating system at all during our Out-of-Box testing. The Overclocked Sapphire HD7870 OC graphics card had fans set to 65% which was just audible over normal operating hum. At these fan speeds under full load the Overclocked Sapphire HD7870 OC Edition's temperature increased to 65C. The graphics card with the maximum overclock was 23C cooler than the AMD Radeon HD6970 under full load and did not emit as much noise. The overclocked Sapphire HD7870 OC graphics card was also 24C cooler than the NVIDIA GeForce GTX570 that had a full load temperature of 89C and more a more audible fan. Source
To overclock the Sapphire HD7870 OC graphics card we are using Sapphire's overclocking utility TriXX. We found the highest GPU core clock without voltage tweaking at 1245MHz. Compared to its Out-of-Box settings this is an increase of 195MHz and 18.6% faster operating frequency. Next we found the highest memory clock which was 1560Mhz. Compared to the stock Sapphire HD7870 OC this is an increase of 310MHz and 24.8% faster operating speed. We increased the slider by 82mV up to 1.3V. The voltage increase allowed an additional 25MHz bringing the highest stable overclock to 1270MHz. The overall speed increase from the overclock on the GPU is 21% faster compared to the Out-of-Box operating speed.
The 7000 series AMD video cards provide better performance than its last generation competition while also being more power efficient. The extra power consumption that the overclock required was still more power efficient than the Radeon HD6970 and GeForce GTX570 with a marginal performance advantage.
Under full load the temperature of the Sapphire HD7870 OC graphics card increased by 37C up to 61 degrees Celsius with fan speeds only reaching 45%. The fans were not audible over the normal operating system at all during our Out-of-Box testing. The Overclocked Sapphire HD7870 OC graphics card had fans set to 65% which was just audible over normal operating hum. At these fan speeds under full load the Overclocked Sapphire HD7870 OC Edition's temperature increased to 65C. The graphics card with the maximum overclock was 23C cooler than the AMD Radeon HD6970 under full load and did not emit as much noise. The overclocked Sapphire HD7870 OC graphics card was also 24C cooler than the NVIDIA GeForce GTX570 that had a full load temperature of 89C and more a more audible fan. Source
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