Display settings / refresh rate

[MarkK]

I have an old Prestigio LCD monitor (model P170T, res. 1280x1024) and up until 9.04, Kubuntu didn't have problems with it. Now it seems to want to set the monitor to refresh rate of 75Hz, despite the fact that it only supports refresh rates up to 70Hz. OK, no biggie, I thought. I open the Settings -> Display and manually set it to 60Hz, which is readily available from the combo box. Click Apply and here we go, right?

Well, no. Not exactly. First, when I click Apply, my 60Hz selection automagically changes to Auto and, secondly, the next time I fire up the computer, the refresh rate is back up at 75Hz, flickering. Very annoying.

How can I solve this problem?

[kevinc]

Re: Display settings / refresh rate

The old way would have been to look at /etc/X11/xorg.conf which now looks something like

Section "Device"
Identifier "Configured Video Device"
EndSection

Section "Monitor"
Identifier "Configured Monitor"
EndSection

Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
EndSection

You might be able to try setting refresh rate in this. If you check the log file in /var/log/Xorg.0.log there may be some clues.

info xorg.conf shows much info, including this

HorizSync horizsync-range
gives the range(s) of horizontal sync frequencies supported by
the monitor. horizsync-range may be a comma separated list of
either discrete values or ranges of values. A range of values
is two values separated by a dash. By default the values are in
units of kHz. They may be specified in MHz or Hz if MHz or Hz
is added to the end of the line. The data given here is used by
the Xorg server to determine if video modes are within the spec-
ifications of the monitor. This information should be available
in the monitor's handbook. If this entry is omitted, a default
range of 28-33kHz is used.

VertRefresh vertrefresh-range
gives the range(s) of vertical refresh frequencies supported by
the monitor. vertrefresh-range may be a comma separated list of
either discrete values or ranges of values. A range of values
is two values separated by a dash. By default the values are in
units of Hz. They may be specified in MHz or kHz if MHz or kHz
is added to the end of the line. The data given here is used by
the Xorg server to determine if video modes are within the spec-
ifications of the monitor. This information should be available
in the monitor's handbook. If this entry is omitted, a default
range of 43-72Hz is used.

[barbolani]

Re: Display settings / refresh rate

Another option that could try is: first, make a backup copy of xorg.conf. Then remove all configuration information (modes, resolutions, frequencies) from xorg.conf in the [Screen] and [Monitor] sections. Restart X and see if it automatically picks up the correct values.

[MarkK]

Re: Display settings / refresh rate

Another option that could try is: first, make a backup copy of xorg.conf. Then remove all configuration information (modes, resolutions, frequencies) from xorg.conf in the [Screen] and [Monitor] sections. Restart X and see if it automatically picks up the correct values.

This is my (current) xorg.conf:

Section "Monitor"
Identifier "Configured Monitor"
EndSection

Section "Screen"
Identifier "Default Screen"
Monitor "Configured Monitor"
Device "Configured Video Device"
EndSection

Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen"
EndSection

Section "Device"
Identifier "Configured Video Device"
EndSection

Section "ServerFlags"
Option "DontZap" "False"
EndSection

As you can see, nothing's hardcoded.

In var/log/Xorg.0.log, the only interesting thing I could find was this block:

(II) RADEON(0): 720x400@70Hz
(II) RADEON(0): 640x480@60Hz
(II) RADEON(0): 640x480@75Hz
(II) RADEON(0): 800x600@56Hz
(II) RADEON(0): 800x600@60Hz
(II) RADEON(0): 800x600@72Hz
(II) RADEON(0): 800x600@75Hz
(II) RADEON(0): 832x624@75Hz
(II) RADEON(0): 1024x768@60Hz
(II) RADEON(0): 1024x768@70Hz
(II) RADEON(0): 1024x768@75Hz
(II) RADEON(0): 1280x1024@75Hz
(II) RADEON(0): 1152x870@75Hz

Where does the 75Hz come from?

Back in the day, when not everything was configured automatically, my xorg.conf contained these lines:

Section "Device"
Identifier "ATI Technologies Inc RV280 [Radeon 9200 SE]"
Driver "ati"
BusID "PCI:1:0:0"
EndSection

Section "Monitor"
Identifier "Generic Monitor"
Option "DPMS"
HorizSync 30-70
VertRefresh 50-160
EndSection

Section "Screen"
Identifier "Default Screen"
Device "ATI Technologies Inc RV280 [Radeon 9200 SE]"
Monitor "Generic Monitor"
DefaultDepth 24
SubSection "Display"
Depth 24
Modes "1280x1024"
EndSubSection
EndSection

I don't know how to make use of this data. If I try to stick it into the current xorg.conf, X doesn't even start.

What I actually wanted to ask was, why, if I manually set the refresh rate to 60Hz by selecting an entry from a combo box, it doesn't stay that way? Why does it switch back to Auto (and back to 75Hz after reboot). What is the point of manual configuration if it is not then taken into account?

[kevinc]

Re: Display settings / refresh rate

I found this, http://www.google.sn/url?sa=t&source...jCAak9nSNUCv6g

It may not answer the question about setting the frequency too high and manual override not staying set, but it may help.

[MarkK]

Re: Display settings / refresh rate

It may not answer the question about setting the frequency too high and manual override not staying set, but it may help.

Do you mean the part about switching to Nvidia? Ha-ha - very funny! I might consider switching to Windows, though. I've just about had it with Linux.

[kevinc]

Re: Display settings / refresh rate

No, sorry, I didn't mean about switching to Nvidia. It was a long post with lots of bits and pieces. I was too lazy to cut and paste all the parts that might have been relevant, but thought that you could copy the whole post and then look at each part and see if there were anything there that might help.

I'm a little disappointed in Kubuntu as I seem to remember the versions where there were lots more options, like setting the frequency of the monitor and it would stay at the frequency you chose; now it seems to be going to everything is automatically detected, which is OK if it is right, but in your case, obviously not then where is the manual override?

Maybe someone else can offer a solution?