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Revision as of 15:38, 8 June 2013 by Ashen (Talk | contribs) (The Unichrome-driver)

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Different Unichrome family display drivers

The VIA proprietary drivers

These are considered unstable and insecure. They are however the only way to get any form of 3D acceleration or even reliable modesetting on certain chipsets, and can be installed using the via-chrome9-dkms, xf86-video-via-chrome9 & via-chrome9-dri packages from the AUR.

The Xorg-driver

The driver that comes with Xorg. Supports VIA CLE266, KM400/KN400, K8M/N800, PM/N800 and CN400 chipsets. Accelerates 2D, 3D, Xvideo and mpeg2 decoding using XvMC. Nowadays the Xorg-driver is mostly unmaintained as the development focus is on OpenChrome-driver.

You can install the Xorg driver with command:

pacman -S xf86-video-via

The xorg.conf driver name is via.

Update: currently (June 2013) this driver can't be found in pacman and AUR repos

The Unichrome-driver

Another driver with the development focus on stability and clean code. Unichrome driver only supports CLE266, KM400, P4M800 and K8M800 chipsets. Does not support accelerated mpeg2-decoding.

You can install the unichrome driver with command:

pacman -S xf86-video-unichrome

Update: currently (June 2013) this driver isn't available in pacman and AUR repos

The xorg.conf driver name is unichrome.

The OpenChrome driver

The most advanced and developed driver for Unichromes. Supports CLE266, KM400/KN400/KM400A/P4M800, CN400/PM800/PN800/PM880, K8M800, CN700/VM800/P4M800Pro, CX700, P4M890, K8M890 and P4M900/VN896 chipsets. Accelerates 2D, 3D, Xvideo and mpeg2 decoding using XvMC. This driver is the way to go if you want to be on the bleeding edge.

You can install the OpenChrome driver with command:

pacman -S xf86-video-openchrome


Black screen when booting from LiveCD

If you experience a black screen when booting from Live-CD, place the following paramenter to the end of the kernel load options (please note that "nomodeset" option probably won't work here):


After installing the system you'll need to blacklist this module. Just create a file /etc/modprobe.d/blacklist.conf with the following line:

blacklist viafb

To enable any of the following options to fix issues, first create a new file 10-openchrome.conf in /etc/X11/xorg.conf.d/:

Section "Device"
    Identifier "My Device Name"
    Driver "openchrome"

If your X-Server shows artifacts and fails to redraw some windows, try disabling the "EnableAGPDMA" option:

Option     "EnableAGPDMA"               "false"

If your machine freeze at startup (GDM) or after login (slim), try adding the XAA option "XaaNoImageWriteRect". Note that this only applies if you are using the XAA acceleration method (configured by the "AccelMethod" option). As of 0.2.906, the default acceleration method is EXA.

Option "XaaNoImageWriteRect"

If you experience significant CPU usage and low UI framerate, try adding:

Option "AccelMethod" "XAA"

Hardware Specific

VIA Technologies, Inc. CN896/VN896/P4M900 [Chrome 9 HC]

The EXA acceleration method may cause significant CPU usage and low UI framerate. Refer to the "AccelMethod" option in the #Troubleshooting section.

Unichrome and OpenGL

OpenGL support for Via's graphic chipsets is seriously outdated. At the moment you will not be able to run more fancy applications, games or compositing desktops like Compiz Fusion that rely on OpenGL as a backend, because the more recent OpenGL extensions are not yet supported in Unichrome 3D driver. You will be able to run simple OpenGL-applications though. The 3D driver for Unichrome is provided by the the DRI project.

Install unichrome-dri, libgl and mesa -packages to get OpenGL to work.

DPMS problems

If you experience problems with DPMS not turning off laptop's backlight, try adding:

Option "VBEModes" "true"

to the device section of xorg.conf.

Hangup on exit

If your computer crashes when closing X, you may try not using vesa driver for kernel console. Just delete the vga stuff from kernel line on grub or append line on lilo.

External Resources