There's going a rumour that AMD is having problems with the AMD-8111 I/O Hub of the AMD-8000 chipset for the x86-64 code-named Hammer processors :
The source of the problem is in AMD-8111’s USB 2.0 controller that works incorrectly in certain cases. The disadvantage seems to be so serious that AMD decided to offer its mainboard partners to utilise an additional USB 2.0 controller from a third-party developer for AMD-8000 based mainboards. To tell you the truth, I wonder, why not to make use of a third-party developed I/O Hub. The Hyper-Transport platform is very flexible, as a result, almost any hub may be installed instead of another. While an additional chip, from VIA, for example, costs money and mainboard makers have to redesign their current PCBs for AMD ClawHammer processors, it is more logical to make the redesign for a new I/O controller only and get rid of the necessity to buy an additional chip.
There are about three month before the ClawHammer processors are set to reach the market, thus, AMD may resolve the current problems and everything will be on track with their I/O Hub.