AMD Radeon HD 6850 and 6870 CrossFire Video Card Review

Overclocking

To overclock the AMD Radeon HD 6800 graphics card series, we used the ATI
Overdrive utility that is part of the CATALYST Control Center. When you
‘unlock’ the ATI Overdrive, you can manually set the clock and memory
settings or let the ‘auto-tune’ utility set the frequencies for you.

Just for fun, we tried out the auto-tune feature to see if it could
really find a stable clock configuration, and it worked in about 15
minutes and did not lock up the system. This utility determines the
highest core and memory clock frequency that is stable and shows you
what the GPU temperature is and how much load the GPU is under during
testing.

Before Auto-tune was run we started out at the default settings of 775MHz on the core and
1000MHz on the memory and was able to reach 840MHz on the core and
1130MHz on the GDDR5 memory. We know auto-tune is a little conservative, so we manually bumped it up another 10MHz and was able to reach 850MHz on the core clock and 1140MHz on the memory. This is a 75MHz overclock on the core and a 140MHz boost on the GDDR5 memory ICs.

To test out the overclock we fired up 3DMark Vantage to see what this overclock was like.

The AMD Radeon HD 6850 Video Card Stock 775MHz/1000MHz:

The AMD Radeon HD 6850 Video Card Overclocked 850MHz/1140MHz:

Running 3DMark Vantage with the Extreme preset we got a
score of X6063. The score went up X6623 3DMarks when overclocked, which
was an improvement of 9.2% with this mild overclock. Let’s see how the AMD Radeon HD 6870 overclocked using the same methods.

The AMD Radeon HD 6870 comes with a 900MHz core clock and 1050MHz memory clock. We ran auto-tune on this card and the program came back saying that it was able to reach 940MHz on the core clock and 1140MHz on the memory. This is a 40MHz overclock on the core and a 90MHz boost on the GDDR5 memory ICs.

To test out the overclock we fired up 3DMark Vantage to see what this overclock was like.

The AMD Radeon HD 6850 Video Card Stock 900MHz/1050MHz:

The AMD Radeon HD 6850 Video Card Overclocked 940MHz/1140MHz:

Running 3DMark Vantage with the Extreme preset we got a
score of X7645. The score went up X8099 3DMarks when overclocked, which
was an improvement of 6% with this easy to do overclocking method. Seeing a nice 6-9% performance gain with pretty much zero effort was nice to see and when we have more time we are sure these cards could be pushed even harder!