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Serious bug in newer nVidia cards VESA VBE (Users)

posted by Laaca Homepage, Czech republic, 18.04.2020, 18:05

I bought a new (quite powerful) notebook and succeeded to install the dual boot Win10/FreeDOS.
It has a graphic chip NVidia RTX 2060.
And it is affected too. I haven't test the patch yet.
And I found other issue - all my programs based on my graphic library VenomGFX have garbaged output.
The reason is formaly correct but strange implementation of VESA standard where length of the scan line is not equal to X-resolution.
For example I set the mode 800x600 16-bit and the pixel (0,0) is on address 0. Pixel (1,0) has address 2 (as we are in the 16bpp mode)
But pixel (0,1) is not address 1600 aka (800 * 2) but on address 2048.
It can be obtained from VESA function 4F01h (BytesPerScanline field) so it is not a violation of VESA standard but it is ugly (I would like to write a czech word "prasarna")
I tried to change the behaviour with the VESA function 4F06h but it does not do anything (I don't know why. maybe is impossible to set less than above mentioned 2048 bytes per scanline). Or maybe is this function crippled - I don't know :-(

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