[coreboot] How to change the device id of a VBIOS

Joseph Smith joe at settoplinux.org
Fri Jun 25 13:35:59 CEST 2010

On Fri, 25 Jun 2010 09:06:23 +0200, Peter Stuge <peter at stuge.se> wrote:
> Bao, Zheng wrote:
>> I am wondering, if I got a Vgabios for graphics card A, can I just
>> change the device ID in the binary file to fit the graphics B?
> If the code is the same, sure.
>> Is there any checksum in the vgabios.bin?
> Yes. Option ROMs follow a well defined standard.
I had to do this to get my i810 vbios running on i810e because they have
different device id's but use the same vbios.
So what I did is just use a hex editor and change the device id to the
correct one. But then SeaBIOS would complain about the incorrect checksum.
I used Kevin's buildrom.py utility which basicly clears the lower 4 bits of
the checksum which should be a 16 bit register at 0x07.
This worked great for me, hope it helps you.

>> Is there a tool to handle it?
> Try tools/buildrom.py in the SeaBIOS repository at
> git://git.linuxtogo.org/home/kevin/seabios.git
> http://git.linuxtogo.org/?p=kevin/seabios.git;a=blob;f=tools/buildrom.py
Joseph Smith

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