Well, i did not know that you are looking for a CPU that is not on the list.
I guess that you know this may void the warranty of the board and the cpu by doing so.
Anyway, check the link below.
The last bios update that had a fix for adding new processor support was Version 6066, Released April 2008.
So i have no idea whether this will be updated or not. It is quite an old board now. Sometimes, even CPU that are not on the list works without/with any error message, but this reduces the life of the board and cpu.
All the best,