You can if you have revision D or E board. Unfortunately, the only way to check this is to take the board out of your case, flip it over and look on the backside in the vicinity of the lowest ISA slot. You will need to use a very bright light to find the letter which is printed several layers down in the board itself. The letter is all alone, no other characters near it.
You need not upgrade the bios if you have a D or E board, but the latest bios, which was released in the last week or two, fixes the misreporting of higher speed cpus when you boot.
BTW, there is a good soyo USENET newsgroup - find it and use it.