Ivy-Bridge cpu may work on the Sandy-Bridge cpu's motherboards but you need to flash the Bios first.
+1 for xtreme5 and Alexoiu
For most of the "6" series boards you will need a Bios update in order to support the 3rd generation Intel® Core™ processors. There are a couple ways that you can get this Bios update.
- You can get lucky and find it on a board in stock. The updated Bios showed up on most boards in January, so there are some "6" series boards out there that have the updated Bios on them. If you are buying locally check before before you buy as the Bios version is generally marked on the box.
- Update the bios by putting a 2nd generation Intel Core processor in the board. If you don't have one I have advised that you look for a local reseller that has one and can update your Bios for you. You can find some local reseller at http://inteltechpros.com/