Dolphin config for Paper Mario TTYD

Hello, please help with config to Paper Mario TTYD on GC. At the beginning of the game i have 100% speed but when i'm playing more it lowers to 50% and i can't play. Specification of my PC:

Intel Core i3-2310M 2.10 GHz
NVIDIA GeForce GT520M
4 GB RAM
Windows 7 x64

Thanks a lot!