Why does my macbook pro not run games at full speed through the whole game?

[The Grantula]

I have been playing resident evil 4 for the gamecube on my macbook pro 15 inch and about halfway through the fps dropped to 50%. I don't know if there are just to many things going on during the game or if its something wrong with my laptop. Also on twilight princess for gamecube i can only reach 50% fps while i see other dolphin users on youtube using older less powerful computers and getting full speed. Would appreciate some help thank you.

2.3Ghz intel core i7
8GB ram
Intel HD Graphics 4000