Re-talk core clock/shader clock
So we can draw a conclusion that 8600GTS and 8500GT after the core clock achieved 550MHz, the performances improve not obvious according to the core clock improving. But if the shader clock goes on improving then the performances also keep improving. So for mid-end and low-end graphics, when the core clock is 600-700MHz, the shader clock the higher the better. While the 8800 series, when the core clock is 550MHz then the shader clock is the higher the better.
HARDSPELL

Zajimavy clanek o vlivu pretaktovani GPU a shaderu na vykon v ruznych hrach.