I'm pretty sure 680i do not support 45nms. P35's were the first.
EDIT: I guess only certain boards with certain BIOS can run it. So I guess we can assume 780i has good support?
According to anandtech, some 680i boards will support 45nm with BIOS flash. and I saw evga 680i A1/T1, 680i LT A1/T1 on the list. Dont have the link but search it on the site and you will find it.
What I want to know is the 780i/750i delayed til Dec like everyone is claiming bc of probs with 45nm chips not running right? Is it still on for Nov 12? Grrr