OCC has published a review on the Sapphire Radeon HD6670
A quote from the article:
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The final GPU core clock I was able to get to was 890MHz, which ends up being about an 11% increase. The memory overclocking was done using the exact same procedures. I was able to arrive at about an 18% increase, which was 1180MHz. To make all of these adjustments, I was using the Sapphire TriXX overclocking utility.
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