I retrieved my vgabios via Linux kernel 3.19 (ubuntu 15.04) using this method - http://www.coreboot.org/VGA_support#Retrieval_via_Linux_kernel ; then I downloaded latest sources of SeaBIOS & Coreboot and built Coreboot using compiled SeaBIOS payload as well as vgabios file ( 1002,990b )
After coreboot installation I have decided to retrieve vgabios again, using exactly the same kernel and OS, and then diff'ed two vgabios files out of curiosity. To my surprise, they are slightly different! vgabios_before.bin - SHA1 checksum: e4d320eb278b0118c46e2e470e7154b12c41966d vgabios__after.bin - SHA1 checksum: a9e2ed569bbaaea283b5380a5f6c44fc4efc3da4 Here is a report about 3 bytes difference between them - http://www.diffnow.com/?report=2kwq3 (wait a few seconds while it loads)
Then I teardown a laptop, and check if vgabios inside coreboot's image (flashed in chip) is 3 bytes different as well, but there was no difference against the original vgabios.
So, it appears that, while loading vgabios from a flash chip, coreboot modifies it slightly. Although this tiny difference is not causing any graphical glitches or problems for me, this could be a result of a bug - which is not necessarily limited to my hardware ( Lenovo G505s ) , and maybe could lead to some other problems
Please tell your opinion, is it a bug or I am wrong at something?
Best regards, Vladimir Shipovalov
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Vladimir