Comment 13 for bug 157213

Binary package hint: xserver-xorg-video-intel

When using the xserver-xorg-video-intel drivers for the Intel 855GM graphics card, the driver attempts to use clock frequencies from the card's BIOS tables. These are known to be wrong (see for instance the old issues with needing to patch the tables to get correct resolutions), and this causes X to set a wrong refresh rate leading to for example a flickering display.

The problem is described by Freedesktop.org[1], and a patch that bypasses BIOS tables for the 855GM is described in the third comment of [1]. In order to enable this patch after recompiling the drivers, one needs to set
Option "ModeDebug" "true"
in the device section of the X.org config. I suppose this could lead to some extra debugging info being printed as a side-effect.

For those looking for a quick fix, I've uploaded a patched version[2]. Apart from that I guess the Freedesktop.org patch should be included into Ubuntu's xserver-xorg-video-intel as soon as possible, as this can be a real showstopper for people with the 855GM, especially taking into consideration the existence of bug #155312 preventing some to use the older i810 drivers for the card in Gutsy.

I can confirm that the patch fixes the problem in my case.

[1] http://bugs.freedesktop.org/show_bug.cgi?id=11917
[2] http://folk.ntnu.no/spreeman/deb/ubuntu/gutsy/xserver-xorg-video-intel/ (see version 2.2.1-0ubuntu9.1)