Actually it isn't on the motherboard it is a riser card that only works with the boards they come with, and still functions just like what you would expect from any other onboard audio solution. In the case of m0uthless's first board,
ASUSTeK Computer Inc. - Motherboards - Maximus Formula
it came with the original SupremeFX,
Quote:
SupremeFX II Audio Card
ADI 1988B 8-Channel High Definition Audio CODEC
Coaxial / Optical S/PDIF out ports
ASUS Noise Filter
whereas the replacement board,
ASUSTeK Computer Inc. - Motherboards - Maximus II Formula
came with the SupremeFX X-Fi version (of which the only thing even remotely X-Fi like about it is it gets to use some of the X-Fi software, other than that it is purely Soundmax audio),
Quote:
SupremeFX X-Fi Audio Card
- ADI® AD2000B 8-channel High Definition Audio CODEC
- Creative X-Fi capability
- X-Fi interface
Coaxial/Optical S/PDIF out ports
Probably why the riser from the first board doesn't work with the second. As I understand them they will only work on the board they came with due to the bios support for them.
If you didn't get the riser card with the replacement, I would confirm with Asus that they aren't inter-changeable and if that is the case request they send you the proper one for the new board.