Known VESA problems and workarounds.

1.  Trident TVGA 8900c says it can do 640x480 and 800x600 in 64K colors without
    a Sierra DAC. Use Alt C from menu and select 1 (256 colors) for proper Targa
    viewing.

2.  Older S3 boards (Orchid Fahrenheit 1280 and Diamond Stealth) return wrong
    bytes/line and mode attributes. Use 'vpic /v' to call VPIC.