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vesa_bios_resolutions

VESA BIOS Resolutions in Linux

Native BIOS Resolutions

The native Video BIOS resolutions can be determined by following these steps:

  1. Install an operating system that uses the grub boot loader
  2. Boot into the grub menu
  3. Press 'c' for a grub command line
  4. Run 'vbeprobe'
VBE version 3.0
0x112: Direct Color, 640x480x32
0x101: Packed pixel, 640x480x8
0x111: Direct Color, 640x480x16

The meaning of these codes is also explained here.

Translating these codes into their Linux equivalents by add 0x200 to them yields the following values:

Hexadecimal  Decimal
0x312        786
0x301        769
0x111        785

Selecting a Resolution from the Linux Kernel

The linux kernel source code documentation file Documentation/svga.txt explains that these codes can be used by the kernel at boot time to select the screen resolution. For example, grub's /boot/grub/menu.lst might be modified by adding vga=769.

title        Debian GNU/Linux, kernel 2.6.22-3-686
root         (hd0,0)
kernel       /boot/vmlinuz-2.6.22-3-686 root=/dev/sda1 ro vga=769
initrd       /boot/initrd.img-2.6.22-3-686

Native Screen Resolution

The first generation Eee PC's have an LCD screen with a native resolution of 800×480. If the operating system outputs a different resolution, the screen will either go blank, show only a part of the output, or compress/stretch the output to fit the screen. In the case where Linux is putting out 640×480, it will be stretched horizontally. When looking at console text, such as is often visible before the X Windows system is running, the text will appear slightly wider than normal and will be blurred by the video hardware in order to stretch it.

Adding Video BIOS Resolutions

So how can the Video BIOS be updated to the native resolution of the screen? There is no VESA code number which denotes a 800×480 screen. Therefore we have to update the Video BIOS using a tool such as 915resolution.

* http://tldp.org/HOWTO/Keyboard-and-Console-HOWTO-16.html
* http://gentoo-wiki.com/Asus_Eee_PC_701#Framebuffer

Adding Video BIOS Resolutions in bootloader

For using 800×480 resolution at boottime Nathan Coulson wrote a 915 hack patch for Grub2 bootloader.

Very important: Messing with bootloader you can get your system to unbootable state. More important is that Grub2 config syntax differs from Grub legacy (used in Xandros) so you have to update config files also or system doesn't boot! (though you can still boot it manually from Grub commandline).

Trying install Grub2 when you are under unionfs you probaply just get your system also to unbootable state. (Howto remove unionfs)

* Nathan Coulson - LFS for the EeePC / 800x480 resolution in the console
* Grub2 CommandList
* Grub2 example config

rio b and you sfr rio b and you numero rio

vesa_bios_resolutions.txt · Last modified: 2012/01/28 09:43 by hello