IBM is also in a position to rapidly increase its production capability, if the demand justifies it.
Add in high end production from the research FAB, and an upgraded Dresden, and AMD has access to more capacity than they were being given credit for.
They are continuing to use UMC to FAB chipsets, and given the price of Opteron and Athlon MP motherboards, AMD is likely getting a helpful revenue stream from UMC production facilities, as well.