A via lançou uma versao nova do driver para essa placa que vc tem (P4M900 chipset VN896 -
http://linux.via.com.tw) e eh especifico para o ubuntu 8.04 lts. Eu tenho essa mesma config que vc tem e estava com problema ate agora (acabei de resolver). Essa solucao de usar o modo vesa ou de usar o uniChrome funciona mas vc fica sem funcionalidade 3D. E nao tem um bom desempenho também.
Minha sugestao eh baixar o driver da via no site indicado acima (entra no site e seleciona para Ubuntu) o arquivo contem as instrucoes de como instalar no readme. Se apos instalar e reiniciar a tela ficar laranja com umas listras (foi o que aconteceu comigo) eh necessario efetuar umas alteracoes no xorg.conf (resolucao, monitor etc). Para instalar esse driver eh so entrar na pasta descompactada e digitar ./vinstall (lembrando que precisa de root para isso entao sudo ./vinstall ) Desculpe caso eu tenha especificado demais, eh que sou novato no linux e esses comandos para mim foram novidade!
O meu ficou assim:
# xorg.conf (X.Org X Window System server configuration file)
#
# This file was generated by failsafeDexconf, using
# values from the debconf database and some overrides to use vesa mode.
#
# You should use dexconf or another such tool for creating a "real" xorg.conf
# For example:
# sudo dpkg-reconfigure -phigh xserver-xorg
Section "InputDevice"
Identifier "Generic Keyboard"
Driver "kbd"
Option "XkbRules" "xorg"
Option "XkbModel" "abnt2"
Option "XkbLayout" "br"
Option "XkbOptions" "lv3:ralt_switch"
EndSection
Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
EndSection
Section "InputDevice"
Identifier "Synaptics Touchpad"
Driver "synaptics"
Option "SendCoreEvents" "true"
Option "Device" "/dev/psaux"
Option "Protocol" "auto-dev"
Option "HorizEdgeScroll" "0"
Option "SHMConfig" "true"
EndSection
Section "Device"
Identifier "Configured Video Device"
Boardname "vesa"
Busid "PCI:1:0:0"
Driver "via"
Option "PanelID" "7" #1280x800, Sigle, Dithering
Screen 0
EndSection
Section "Monitor"
Identifier "Configured Monitor"
Vendorname "Generic LCD Display"
Modelname "LCD Panel 1280x800"
Horizsync 31.5-50.0
Vertrefresh 56.0 - 65.0
modeline "1024x768@60" 65.0 1024 1048 1184 1344 768 771 777 806 -vsync -hsync
modeline "1280x800@60" 83.91 1280 1312 1624 1656 800 816 824 841
Gamma 1.0
EndSection
Section "Screen"
Identifier "Default Screen"
Device "Configured Video Device"
Monitor "Configured Monitor"
Defaultdepth 24
SubSection "Display"
Depth 24
Modes "1280x800@60" "1024x768@60" "800x600@60" "800x600@56" "640x480@60"
EndSubSection
EndSection
Section "ServerLayout"
Identifier "Default Layout"
screen 0 "Default Screen" 0 0
Inputdevice "Synaptics Touchpad"
EndSection
Section "Module"
Load "glx"
Load "GLcore"
Load "v4l"
EndSection
Section "device" #
Identifier "device1"
Boardname "vesa"
Busid "PCI:1:0:0"
Driver "via"
Screen 1
EndSection
Section "screen" #
Identifier "screen1"
Device "device1"
Defaultdepth 24
Monitor "monitor1"
EndSection
Section "monitor" #
Identifier "monitor1"
Gamma 1.0
EndSection
Section "ServerFlags"
EndSection