Comment 109 for bug 6270

I'd suggest looking at these release news:
http://lists.freedesktop.org/archives/xorg-announce/2007-November/000430.html

There is one significant line by Eric Anholt:

Disable TV/VGA output on the CH7017/7018 devices.

I think the i855GM TV-OUT was left for dead there. There is currently a ch7017 and ch70xx driver for DVO, but I am getting a bit confused so I don't know if my hardware has a DVO or a TV-OUT (it has a VGA output and a 5pin S-Video output), I'd say the TV-OUT (S-Video output) is the part dismantled in current driver.