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-   -   xorg doesn't set refresh rate properly (

lord_didger 12-17-2007 01:16 PM

xorg doesn't set refresh rate properly
I have LCD Monitor Samsung SyncMaster 710N. I have been using it for about 4 years. Unfortunately recently the monitor has been working improperly. I can open X session in linux and work as usual, however, when I reboot or simply exit from X the screen goes black. Of course this happens when I work in X for a while.

This became a big problem for me because I am not able to use my computer. The monitor is frankly speaking corrupted. The problem remains even when I launch windows. This is definately to do with hardware. However, I can use monitor again after it is 10 minutes unplugged.

I noticed that when I start X the refresh rate is very high - in 1240x1024 mode it is 81 Hz - maximum value. There is no way to change it to something like 1240x1024 @ 60. I tried gft and reconfigure the xserver-xorg but it didn't help.

Moreover, I thing that because of the problem with setting the proper resolution and refresh rate my hardware doesn't work fine.

What should I do to set these parameters correctly?

tyggna 12-17-2007 10:28 PM

Best bet
Your best bet would be to edit /etc/X11/xorg.conf directly. Under the Monitor section add:


VertRefresh "#"
where the # can be either a single number or a range (e.g. 54-63). Once you've done this, and saved your xorg.conf (back it up before you do this), press ctrl-alt-backspace and see if that does the trick.

lord_didger 12-18-2007 03:57 PM

Thanks for answer. Unfortunately it doesn't work. I modified my xorg.conf but the Vertical refresh is still 75 Hz

My xorg.conf looks like that:


Section "Files"

Section "InputDevice"
Identifier "Generic Keyboard"
Driver "kbd"
Option "CoreKeyboard"
Option "XkbRules" "xorg"
Option "XkbModel" "pc105"
Option "XkbLayout" "pl"

Section "InputDevice"
Identifier "Configured Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/input/mice"
Option "Protocol" "ImPS/2"
Option "Emulate3Buttons" "true"

Section "Device"
Identifier "nVidia Corporation NV31 [GeForce FX 5600]"
Driver "nvidia"
BusID "PCI:1:0:0"

Section "Monitor"
Identifier "SyncMaster"
Option "DPMS"
HorizSync 30-81
#VertRefresh 50-60
VertRefresh 60
#1240x768 @ 60 Hz (GTF) hsync: 47.70; pclk: 77.46 MHz
ModeLine "1240x768_60.00" 77.46 1240 1304 1432 1624 768 769 772 795 -HSync +Vsync

Section "Screen"
Identifier "Default Screen"
Device "nVidia Corporation NV31 [GeForce FX 5600]"
Monitor "SyncMaster"
DefaultDepth 24
SubSection "Display"
Modes "1280x1024" "1152x864" "1024x768" "800x600" "640x480"

Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
InputDevice "Generic Keyboard"
InputDevice "Configured Mouse"
What else can I do?

tyggna 12-19-2007 10:09 AM

monitor options
For Linux, that's really it.

Now, most monitor's are "smart"--meaning they can tell your graphics card what kind of refresh rate they need. Chances are, if you're still getting 81hz after changing xorg.conf, then something is set on your monitor to override this. Try going into your monitors onboard configuration and see if you can find anything.

If you can't--then changing your monitor driver to "generic" instead of syncmaster--or whatever it is now--would cripple the monitor's ability to override your settings.

lazlow 12-19-2007 01:03 PM


ModeLine "1240x768_60.00" 77.46 1240 1304 1432 1624 768 769 772 795 -HSync +Vsync
Shouldn't that be 1280X768?

2nd. That is only 1/2 of what you have to do. You forgot to add it to your modes line.

Modes "1280x1024" "1152x864" "1024x768" "800x600" "640x480"
Should be:


Modes "1240x768_60.00" "1280x1024" "1152x864" "1024x768" "800x600" "640x480"
Good luck.

lord_didger 12-19-2007 03:17 PM

lazlow tyggna
tyggna, you advised me to change the monitor's driver. I did't know what you mean so I changed my graphic card's driver. It was set to nvidia - now is nv. That helped. When I change the value of VertRefresh it really works. I checked it in the monitor's onboard configuration.

lazlow, you're absolutely right. It was mistake. I wonder why I thought that 1240x768 was a proper mode?

Do you know why the previous driver doesn't follow the options set in xorg.conf? I typed nvidia-installer --version and I got


nvidia-installer: version 1.0.7 (buildmeister@builder3) Wed Jun 13 18:39:37 PDT 2007
The NVIDIA Software Installer for Unix/Linux.

This program is used to install and upgrade The NVIDIA Accelerated Graphics Driver Set for Linux-x86.

Copyright (C) 2003 NVIDIA Corporation.
This driver is quite new. I remeber that I compiled it a few months ago after I downloaded it from

lazlow 12-19-2007 03:38 PM


You have to add both the lines I referred to in post #5. The names in quotes have to be EXACTLY the same in both places or xorg will not understand.

I do not know where it is in Debian but in RH based distros there is also a monitor config file. Post #4 has the right idea on this.

Electro 12-19-2007 11:50 PM

All monitor settings and desire modelines should be in the monitor section in /etc/X11/xorg.conf.

The driver nvidia does use the settings but ignores them when EDID is enabled which is set to enable by default.

I suggest reading nVidia's documentation for Linux module (driver). It explains about modelines. gtf utility, metamode, and several others.

lord_didger 12-20-2007 10:17 AM

You've said that EDID is enabled by default. Can I set an option in xorg.conf to disable it? I found nothing about EDID in `man xorg.conf`.

GlennsPref 01-14-2008 08:47 PM

see this post to disable EDID.

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