server 1.5pre + mga driver, sets illegal modes for monitor

steve tell tell at
Wed Jun 18 12:08:18 PDT 2008

I'm having a problem where the X server in conjunction with the "mga" 
driver sets illegal modes for my LCD monitor.


Fedora 9, with current updates; kernel 
Matrox G550 video card; dual port with DVI and VGA connectors
Viewsonic VP191b lcd panel  (both DVI and VGA connectors)

The cleanest of many configurations I've tried is connecting the monitor 
to the video card with a DVI cable, and having no xorg.conf file at all.

As seen in the attached log (Xorg.0.log), an EDID is recieved from the 
monitor.  It has reasonable-looking monitor info, and everything else in 
the log looks normal.

It isn't obvious from the log what mode is being chosen, but the monitor 
doesn't like the result.  The monitor stays blank except for its
on-screen display, which says:
 	"Out of Range
 	H. Frequency 30 kHz
 	V. Frequency 28.2 Hz"

I have also tried connecting the monitor with only a 15-pin analog VGA 
cable.  Over the VGA connection, DDC does not work, so no monitor info is 
recieved by the X server.

If I use the VGA connection and start X with either no xorg.conf or with 
the fedora-default very simple one, it falls back to 800x600, which _is_ 
correctly displayed on the monitor.

But if I try to force the monitor's preferred 1280x1024x60Hz mode, either 
by setting HorizSync and VertRefresh and specifying Modes, or by 
specifying an explict Modeline, I again get a blank screen with and "Out 
of Range" message from the monitor's on-screen display.

I can post assorted xorg.conf and log files for this configuration too, if 
it would help.

The previous working distro on this machine was Fedora Core 4, which of 
course had a much older X11 (Xorg 6.8.2, I think) - but it had no trouble 
driving the same card and monitor.

It appears that somehow X is computing bad display modes for me, whether 
it builds them from EDID information or from information in the xorg.conf 
file. But when it sets the default 800x600, it is able to do so correctly, 
which suggests that the actuall mode-setting code is working.

Any suggestions?

How do I tell from the log file (or elsewhere) what mode the X server 
thinks it has set a screen to at any given instant?


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