[coreboot] Change vga bios timing

Piero mercurio_5a at yahoo.com
Fri Aug 30 08:42:11 CEST 2013

Hi all,

After some search on internet and on the coreboot wiki and forum, I decided to buy the E350m1 Asrock motherboard that seems to be full supported from coreboot community.

But I'd like to modify the bios and/or the vgabios to use with an old CGA/EGA monitors that work with an HSYNC at (about) 15kHz despite the VGA at 31kHz.

I found some interesting project on internet (1 free and 1 commercial), i.e. :


where the author has modified the Award 4.51pg bios to replace the vga table written by the video card in RAM with a modified version (different vgatable timings).

Or i.e. this commercial project:


where the author has modified the ati bios to force the card to work at other horizontal frequencies.

I'd like to ask you if it is possible to do with coreboot the first example above.
Somebody can advise me where to start?

Now, I'm following the second example above in fact, I started to disassembly the AsRock E350m1 video bios (pci10029802.rom) and I identified the asm code part where the resolutions are set; but at the moment I was not able to find the vga table inside the hex in order to change the timing.

Some help? :)

Thank you very much

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