Add Rom to ASROCK 775S61 BIOS seems to be impossible!!

I'm trying to add a rom chipset of VIA6421A controller to the bios of my motherboard.
It is an Asrock 775S61.
Impossible to open the original bios i attached here with any software.
Tried all the version of mmtool that has always worked fine for other bios.
The same for the rom bios of my raid controller (attached here too).
I verified the asrock bios attached installing it on the motherboard and all work fine!

can someone help me to add the Via rom in the bios attached?

Regards

  775S61.rom (Size: 256 KB / Downloads: 0)

  6421V431.rom (Size: 62 KB / Downloads: 0)