Looks like if you've got a K8T890 board, you're going to be SOL if you're planning to upgrade to an X2 chip when they become available. Well, maybe not SOL, but you're going to have to buy a new mobo ;)

"It is unclear what the exact reason behind incompatibility of VIA’s core-logic and AMD’s dual-core processors is. AMD Athlon 64-series processors use Hyper-Transport bus, which is an industry standard that does not change from revision to revision, that ensures interoperability between variety of mainboards and processors, even despite of actual speed-bin."