Sorry, since I don't have that MB there really is no way for me to know what utility will properly update that RSDT.
This is what one user that successfully Flashed a P5E3 Mod stated on a different Forum:
"Sloution Found:
The solution is to use afudos utility with /pbnc /n options. Also the bios has to be flashed twice: first the original bios and then the moded bios of the same version.
Hope this is usefull. "
So it looks like you have to flash like this with the Unmodified and the Modified Bios with Afudos 2.x:
Afudos /ixxxx.rom /pbnc /n
This is what one user that successfully Flashed a P5E3 Mod stated on a different Forum:
"Sloution Found:
The solution is to use afudos utility with /pbnc /n options. Also the bios has to be flashed twice: first the original bios and then the moded bios of the same version.
Hope this is usefull. "
So it looks like you have to flash like this with the Unmodified and the Modified Bios with Afudos 2.x:
Afudos /ixxxx.rom /pbnc /n