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On the Vortex86DX, installing the LCD BIOS ROM changes the way the display works in all modes. Even under the BIOS, or DOS, the screen is (for example) 800 x 600, and software driving it in a “standard” BIOS text mode will appear in the centre portion of the display.
To build an image for CE, the BSP offers only catalog settings for LCD bit depth, not screen resolution, use 16 bpp.
In summary, for the Vortex86DX, screen resolution is fixed and determined entirely by the BIOS, and cannot be over-ridden, only broken, by bootloader settings.
The Vortex86DX2 behaves differently, both in the way it displays text screens and the way it is handled by CE.
Installing the LCD BIOS ROM does not change the way the display behaves at boot. The BIOS screen, DOS and CE bootloader text are displayed “full screen” – the screen seems to continue to operate at 640 x 480.
To build a CE image, the BSP offers two LCD settings 1024×600 or 640×480, or VESA BIOS 2.0-Compliant, use the VESA BIOS setting.
By modifying the bootloader screen settings, the Vortex86DX2 resolution is variable rather than being fixed by the BIOS, and for CE at least is controlled by the bootloader settings.
Application note provided with thanks by Tony Hedge – Bethnic Sciences