OSDev.org

Does anybody know where I can find a tutorial about vbe?? I need to acces it in protected mode? I wanted to find the entry point but couldn't find. I know it's there because when I tried it in real mode it worked but not in protected mode.

So if anybody knows a tutorial about vbe in protected mode, help me!!

btw: I use C as my language and a little bit of assembler

hi,

Dear friend just because vbe works in real mode it does not mean your ROM will have Pmode entry point(PMID). This is because VESA VBE 2.0 & 3.0 mentions that the Pmode entry point is only optional (Though real mode int 0x10 (0x4Fxx) is a must for compliance).

You must check whether your video card is VESA 2.0 compatible.

As for scanning do this: I assume you have linux

1) Try to dump the first 1Mb of your memory using 'dd'
2) Use a hex editor like KHexedit to check for PMID signature.

Alternately try to scan for PMID from 0xC0000 - 0xF0000 (I found mine to be at 0xC3800).

Hope this helps.

regards
Gandalf

And even if it's there, It is set up to be used from 16bit pmode, You are better off going to unreal mode ,switching vesa mode, Then coming back to pmode.

ASHLEY4.

thnx, fortunately I have Linux

Yes, that would be an option to but I read in the source code that comes with the VESA VBE specs that if you want to do plot a pixel you must do a bankswitch (I think, don't know actually) but isn't this in real mode??

hi,

Yes if you use bankswitch mode u will have to switch to real mode every now and then (Which in my view is an avoidable overhead).  We used Linear Frame Buffer mode for our os (Dynacube OS). And now we don't have to switch banks. But the other problem that comes with LFB is that your GUI might not work with older video cards that donot support LFB.

regards,
Gandalf.