VideoBios Vesa table

[Kova78]

Hello guys,I'm studying the Video Bios and the Vesa standards
My aim is trying to figure out how this guy has reversed and forced the X550 Ati video card to work (in native mode) with other video resolutions and specially with other Hsync freq. (in order to use with the old Arcade monitors):
http://tinyurl.com/mgcqnar (scroll down to see all the supported video resolutions).After reading ton of documentations found on google, I started to reverse, with IDA, the X550 Ati video card bios (that I attached), but at this moment it is very hard to me to find the VESA table presents inside (I have experiences on reversing, but never with the bios).Somebody, smarter than me , would explain how to find the table inside the Vbios? How to interpret it?
In fact, I noticed that the vesa table format changes despite the producer: ati, nvidia etc.
After that I want to modify the crtc register in order to change the hsync frequenciesP.S.
This guy did something that I'd like to do: http://tinyurl.com/m4w42rt (I translated it in English, with google ).Please help me
Thank you in advance for any response

SapphireX550.zip

Bios.zip

Edited September 17, 2013 by Kova78

[kao]

Looking at static disassembly is a last resort. You can spend days and still find nothing. I think I was able to locate function that RayeR calls VBE_ReturnControllerInfo in your BIOS and a small table with few VGA modes but that's all.

 

It would be much easier if you started with gathering information, eg. which modes are currently supported by your card. Then try to locate those numbers in BIOS diassembly.

Locating handlers of each VESA call using debugger would also help a lot. That would require you to learn how to use DOS and some ancient debuggers, however..

 

TL;DR - it's a very specific task and requires specific skillset. I believe guys at VOGONS or other specialized forum could help you better than the guys here. 

 

Thanks for bringing me 15 years back in time,

kao.

[Kova78]

Looking at static disassembly is a last resort. You can spend days and still find nothing. I think I was able to locate function that RayeR calls VBE_ReturnControllerInfo in your BIOS and a small table with few VGA modes but that's all.

 

It would be much easier if you started with gathering information, eg. which modes are currently supported by your card. Then try to locate those numbers in BIOS diassembly.

Locating handlers of each VESA call using debugger would also help a lot. That would require you to learn how to use DOS and some ancient debuggers, however..

 

TL;DR - it's a very specific task and requires specific skillset. I believe guys at VOGONS or other specialized forum could help you better than the guys here. 

 

Thanks for bringing me 15 years back in time,

kao.

 

Thank you Kao for your response :-).

I posted the same thread to Vogons, but at the moment nobody has responsed

In which manner can I locate the handlers of each VESA call? ?

 

If you are courious attached to my first post you also find the modified bios of the video card proposed in my first link .

 

Thank you

Bye

[PeterPunk]

Mission accomplished!!!

 

@Kova78, I guess this info will interest you:

Yesterday I managed to modify the AVGA 5000 BIOS to run on any 5450.

 

Regards.