"When it came down to the overclocking of the Sapphire HD6790, I was able to get the GPU clock speed all the way up to 1000MHz, which is about a 19% overclock on the GPU core with no voltage adjustments. I was able to get the clock speed a little bit higher, however it was not stable enough to run all of the benchmarks in the OCC benchmarking suite. The memory was a little bit more tricky to overclock on this card, I was trying to get up around 1250MHz, however anything that I set above 1235MHz was unstable and would give me artifacts on the screen, so I had to back my clocks down to 1230MHz. That is, however, about a 17% increase on the memory. Overall the overclocking of the Sapphire HD6790 was just like any other video card when it comes to the clocking with out using an voltage adjustments."
Any major computer upgrade generally requires a full software reinstall too. No so if you heed the advice in the guide to Upgrading a Motherboard without Reinstalling. PCSTATS Tips