My full system specifications -
Intel i7-860 processor, Asus P7P55D motherboard, OCZ Gold 8GB DDR3-12800 RAM, HIS HD 5850 1GB DDR5 graphics card, onboard sound card, Corsair 650W power supply.
What dipankar2007i said was really useful - I never thought of that, rather, I should not be thinking about that since the game software should take care of that issue. I am currently away, so over the weekend, I will test the solution.
I already mentioned that FIFA 2010 has really subpar graphics - I disagree with dipankar2007i here that people don't play FIFA 2010 for graphics. No game is played "FOR" its graphics, they are almost always played for the experience and if the graphics are bad or are stuttering as in case of this game, the experience is ruined. It is a viscious circle, really. There are no issues with me playing FIFA 2010 on 5850, either.
I will post the results after I try using all the cores. That said, I experienced FIFA 2011 demo has much better graphics. But the momentary stutter is still present - hoping the same "affinity" fix works for it.