You have bumped the other thread that has plenty of information, replies and views. There is no need to create another thread. I'll lock this one down.
AC3 is incredibly CPU bound. It is also a port from a console game. I believe a lot of this has already been covered in the other thread. When the game was newly released (and the other thread current) the issue was investigated, and it was determined that a driver fix could not resolve the issue.
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