Via vt6421 bios on Lan card bootrom

[cisy]

Hi,

I am trying to make my vt6421 card boot. The card itself has a bios chip soldered on it, but it doesn't work.
My mobo is an old asus cuple-vm (socket 370). I cannot mod the motherboard's bios, so I thought of using lan card bootrom as a carrier for
this controller's bios. I want to flash my realtek NIC bootrom chip with 6421V431.rom file, that I found on the internet.

What do You think of it? Will it work?

Also I looked into this file with a hexeditor and it looks a bit different from other pci roms eg. gpxe, plop manager etc
These are the first bytes of the file:

55 AA 7C E8 16 4C 0B 00 00 ...

The 7th byte has a value of 0B. I read somewhere that this is the checksum byte and it should be equal to 0, otherwise the rom isn't recognised as a proper rom. Maybe that is why it doesn't show on boot?! Can someone confirm this? Is there a way to mod this bios?

I know that for this to work I need to change vendor and device ids in the bios to my NIC's. How do I recalculate the checksum after that?

Respects
Arek