There's a rumour on the internet, that AMD will change the current CPU revision E3 used in the socket 939 processors 3000+ - 3800+ to E6. All existing socket 939 based mainboards will be supported, but a BIOS update is required to recognize the new CPUs.
A reason for the new revision isn't known yet, possibly AMD has discovered a minor fault in the current revision which will be fixed in the new one.

*Update*
Our colleagues of planet3dnow.de report that the Athlon64 boxcode change from ADA3X000BPBOX to ADA3X00BWBOX. And also the Sempron models 2600+, 2800+, 3000+, 3100+ and 3300+ change to the new revision E6 (SDAXX00BOBOX - > SDAXX00BXBOX) which is probably a hotfix, but don't say the reason.