Actually they didnt need ATI at all. They could have done like Intel. Tho Intel now targets more than "fusion". The target now is also nVidia and high margin performance cards.

So they basicly payed 5.5billion for something they could have used a few 100mil (worst case) or less to develop inhouse.
I´m sure people thought they bought a glooming business that could make a profit. But it was a shame that ATIs main revenue and profit was Intel chipsets.