neomagic blank screen in 16bpp mode

[Kacper Wysocki]

On 8/2/06, Kacper Wysocki <kacperw at online.no> wrote:
> I have an aging IBM Thinkpad 240 with a Neomagic MagicGraph 128XD
> video card onboard running an updated debian sid with X.org 7.0.0.
> Recently I updated my system and at the same time added a modeline to
> xorg.conf, and now startx gives a blank screen - the machine responds
[snip]
> Is it possible that I somehow damaged 16bpp mode on my video card with
> an out-of-spec Modeline? (doesn't make much sense, since fbdev works
> in the same mode)
[snip]
> My xorg.conf and log files can be found at
> http://kacper.doesntexist.org/linux/neomagic/xorg.conf
> http://kacper.doesntexist.org/linux/neomagic/Xorg.0.log

I realize now that this list isn't a good place for support-related
questions (but there is no other list that is a better match).
However, it may be interesting to hear how I resolved this issue.

I noticed how the fbdev driver's 800x600 default autodetected modeline was
Modeline "800x600"   36.00  800 824 896 1024  600 601 603 625 +hsync +vsync

While the neomagic driver was printing the following default modeline
in the log file:
 Modeline "800x600"   40.00  800 840 968 1056  600 601 605 628 +hsync +vsync

So I took the former and stuck it in my xorg.conf, and voila things
were back to normal. What's interesting and strange is that things
used to work without a modeline in xorg.conf, as if out-of-spec
modelines "stick" to mode autodetection across X server restarts...

Regards,
 -Kacper