Overclocking Sapphire HD4850 but no performance

I have Sapphire HD4850 and i have tried to overclocked my graphics card recently. I used Catalyst Control Center for overclocking.I have both Core Clock and Memory Clock increases with very small increments starting. Then I run Far Cry 2 benchmark.but with increased values of overclocking both are average that minimum and maximum values of the images per second is lower than on standard settings. whats wrong here ? can some one solve this problem ?

If the bar is higher, the chip is also warmer when the security mechanism is too warm may be the card for self problem. Time the clock rates observed under load?

try with the Riva Tuner overclocked try to the maximum value of FPS have increased, the minimum value of 3 FPS in comparison with the values at standard clock fallen. Will Crysis equal times, because it is a benchmark tool that can help.