Diamond Viper V770 Ultra Review
The Viper V770 Ultra's default clock speeds are a core of 150MHz and memory of 183MHz.  As I stated in the introduction, there are no gurantees when it comes to the how high a particular card can be overclocked.
While I was able to run all the benchmarks in the review at overclocked speeds of 175MHz/200MHz, I reached 179MHz/210MHz successfully benchmarking GLQuake, but Quake 2 caused a system lock up.
These charts show the percentage gain in frames per second by overclocking the Viper V770 Ultra from 150/183 to 175/200.  In lower resolution modes such as 640x480 and 800x600 the gains were minimal.  At higher resolutions, overclocking started paying off with increased performance.
However, the gains are dependent on amount of the stress a benchmark is putting on the graphics sub-system as illustrated by the results of the Quake 2 demo1 versus the Quake 2 crusher.  The charts also indicate that overclocking provides better results when running in higher resolutions and/or 32-bit color.
Overclocking - 16-Bit Color
Overclocking - 32-Bit Color
Next: Benchmark Conclusion