If you own a P5B, P5W, P5K or P5N board, then it's very likely that your board will work with the new 1,333MHz FSB processors. The Commando and Striker series of boards are also supported. The new BIOS versions for these boards will add support for the Core 2 Duo E6850, E6750, E6550, E6540 and Core 2 Extreme QX6850.
It's great to see when a company responds quickly to a new product release and offers BIOS upgrades to make older product compatible. We'd expect to see BIOS upgrades become available from other motherboard manufacturers shortly as well, although some P965 and 975X boards might not be able to work with the new 1,333MHz FSB.
"As the leading motherboard manufacturer, our customers have come to expect the latest solutions from us," said Joe Hsieh, Director of ASUS Motherboard Business. "Our series of Core2 Extreme/Core2 Duo 1333FSB-ready motherboards once again proves our leadership position for the newest and most advanced processors."
You can find the complete list of supported Asus boards here, just be aware that some of the links don't link to the correct products, so you might have to find your board and then the correct BIOS.