G550 dualhead with different resolutions

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G550 dualhead with different resolutions

Postby mithi » Wed Dec 26, 2007 4:46 pm

I'm using a G550 dual DVI PCIe and a Nvidia gf6600 to support three displays (two Samsung Syncmaster 204B/20"/1600x1200 and one Samsung Syncmaster 940B/19"/1280x1024). The G550 is connected to one 204B (port A, using DVI) and the 940B (port B, using DVI) and thus has to use two different resolutions. However the G550 produces a signal at port B that matches the format used at port A, even though the Xorg.log shows that the supported modes are correctly read from the monitors. The on screen display of the monitors show that the 940B is fed a 1600x1200 signal.

This results in unreadably distorted output on the 940B. Reducing the resolution of the 204B at port A to 1280x1024 solves this. Other combinations of different resolutions (1600x1200, 1280x1024, 1024x768) show that port B produces a signal that matches port A every time and distorts the second display in a characteristic way.

Is that a known problem and does there exist a solution to that? I'd really like to have each display at its respective maximum resolution.
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Postby tuxx-home.at » Wed Dec 26, 2007 9:29 pm

Hmm, that's strange, especially because your logfile states that the desired
resolutions are getting accepted by the driver (first screen is set to 1600x1200
and second screen is set to 1280x1024).

Have you tried this configuration in a dualhead setup where the nvidia card
is not configured? Just to make sure that the nvidia driver doesn't break up
stuff...

Have you tried to use specific modelines for your monitors, e.g. the following
DDC gathered modelines for the first screen on the mga card:

Code: Select all
Modeline "1600x1200"x0.0  162.00  1600 1664 1856 2160  1200 1201 1204 1250 +hsync +vsync
Modeline "1600x1200"x59.9  161.00  1600 1712 1880 2160  1200 1203 1207 1245 -hsync +vsync


and the following ones for the second screen on the mga card:

Code: Select all
Modeline "1280x1024"x0.0  108.00  1280 1328 1440 1688  1024 1025 1028 1066 +hsync +vsync
Modeline "1280x1024"x59.9  109.00  1280 1368 1496 1712  1024 1027 1034 1063 -hsync +vsync


Don't forget to refer to the Modelines by their name as stated in the Modeline
command, e.g.:

Code: Select all
Section "Screen"
   [...]
   SubSection "Display"
      Mode "1280x1024"x59.9
   EndSubSection
EndSection
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Postby mithi » Wed Dec 26, 2007 11:36 pm

tuxx-home.at wrote:Hmm, that's strange, especially because your logfile states that the desired
resolutions are getting accepted by the driver (first screen is set to 1600x1200
and second screen is set to 1280x1024).
That made me wonder, too.

tuxx-home.at wrote:Have you tried this configuration in a dualhead setup where the nvidia card
is not configured? Just to make sure that the nvidia driver doesn't break up
stuff....
I did and the problem remains.

tuxx-home.at wrote:Have you tried to use specific modelines for your monitors, e.g. the following DDC gathered modelines for the first screen on the mga card:
The signal still follows the first screen.

Tomorrow I'll check if I can use the two 20" displays on the mga card and the 19" on the nvidia card. If that works the solution for lazy/rich people is replacing the 19" display with another 20" display ;)
Finding a solution where the two different resolutions would be displayed by the mga card would be optimal.
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Postby tuxx-home.at » Thu Dec 27, 2007 12:40 am

The signal still follows the first screen.


That's really weird, I've never heard about this.
What's the BIOS version on this card? Have you checked/upgraded it using
the mga bios update floppy available from here?

[http://matrox.tuxx-home.at/viewtopic.php?t=27]

Another thing that comes to my mind is setting the Matrox card as primary
display adapter in your system BIOS (if possible). Currently, the nVidia
card is the primary display adapter and that _SOMETIMES_ causes troubles
in combination with Matrox cards, although I never heard about this being the
cause for your problem, but it's worth a try.

You can check the primary display adapter settings in your Xorg.0.log file
after you tried to modify it. The Matrox card should have the '*' symbol
in the PCI listing output in front of it. Currently, the nVidia card is the
primary display adapter in your system, thus your output looks like this:

Code: Select all
(--) PCI: (3:0:0) Matrox Graphics, Inc. MGA G550 AGP rev 1, Mem @ 0xbc000000/25, 0xfa8fc000/14, 0xfa000000/23, BIOS @ 0xfa8c0000/17
(--) PCI:*(4:0:0) nVidia Corporation NV43 [GeForce 6600] rev 162, Mem @ 0xfd000000/24, 0xc0000000/28, 0xfc000000/24, BIOS @ 0xfe9e0000/17
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Re: G550 dualhead with different resolutions

Postby tuxx-home.at » Mon Feb 11, 2008 9:40 am

Did you make any progress in solving this issue by now?
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Re: G550 dualhead with different resolutions

Postby tuxx-home.at » Wed May 07, 2008 8:51 pm

Today, svenx posted some very important information about your display (the Samsung 204B). It turns out that this special monitor has problems when connected via DVI, so please have a look at the following thread for detailed information about how to work around this issue:

[http://forum.tuxx-home.at/viewtopic.php?f=1&t=544]
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