FPS drops on some games

I have problem with some games. For exemple, i have slowdown on mario kart wii especially on menus like the chose tracks menu and at the start of a race. I think my computer is fast enough because i can a lots of pc game with ultra setting without fps drop.

The game is unplayable on dolphin 4.01 it is too slow and it is playable but with some fds drops un dolphin 3.5.


Specs


CPU: AMD Vishera FX-6300 3.9ghz(OC)
RAM: 8go 2133 mhz
GPU: AMD Radeon HD7700