Newsgroups:	comp.os.msdos.djgpp
From:	adam AT videodatasys DOT com (Adam Meyerowitz)
Subject:	VGA,PCI and Dos Extender
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Date:	Tue, 5 Jan 1999 14:27:26 GMT
To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Hello,

Maybe someone can shed some light on this.  I'm programming in a dos 
extender (Pharlap TNT RealTime) and trying to write to a PCI VGA card
by mapping the linear frame buffer into the programs data segment.
Basically this is what I do.

1.	Get the Physical Address Pointer to the linear frame buffer
	by using a VESA call.  I confirm this is correct by comparing
	it to the value returned from PCI Bios Calls.

2.	Map the linear frame buffer into the program's data segment
3.	Change the video mode by using VESA Calls (4f02 or something
	like that).

4.	Use the pointer returned from 2 to write into the memory.

All this sounds correct but nothing happens besides the change of the
video mode.  I cannot see any output on the vga.

Any hints or suggestions?

Thanks
Adam Meyerowitz
Video Data Systems

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