Emulator

I was playing LoZ: Wind Waker (GZLE01) in Dolphin 3.0-201 64 bit, mamario's build. I was experiencing slowdowns whenever there is fog, and figured this was because I didn't have a powerful enough machine, so I decided to disable it alone rather than lower the entire game's graphic quality. However, even after enabling Disable Fog option in the Graphics Settings there was still fog present in-game, with the notable examples of Forest of Fairies and the Forsaken Fortress.
As far as I can tell, this issue is consistent with the Dx9 and the Dx11 renderers. I didn't try the OpenGL renderer nor the Software renderer. I have only tested it using the JIT recompiler.

My setup is:
OS: Windows 7 SP1 64 bit
CPU: Intel i7-920
GPU: ATI Radeon HD 5850
RAM: 6 GB DDR3-1600