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  #1  
Old 23rd December 2007, 07:37 PM
mediator Offline
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Cannot set refresh rate to 75 or 85 Hz?

Hi,

I recently installed Fedora 8. But the screen refresh rate doesn't goto 70, 75, or 85 Hz. If I do that, the screen goes blank and then prompts with the same 60 Hz. AS a result, I can see the flickering.

How can I set the refresh rate to above 75 Hz?

Here's the content of xorg.

Quote:
# Xorg configuration created by system-config-display

Section "ServerLayout"
Identifier "single head configuration"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
EndSection

Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbModel" "pc105"
Option "XkbLayout" "us+inet"
EndSection

Section "Monitor"
Identifier "Monitor0"
ModelName "Monitor 1024x768"
HorizSync 31.5 - 61.0
VertRefresh 50.0 - 75.0
Option "dpms"
EndSection

Section "Device"
Identifier "Videocard0"
Driver "sis"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Depth 24
EndSubSection
EndSection
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  #2  
Old 23rd December 2007, 09:25 PM
pete_1967 Online
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You can only use resolutions and refresh rates that both your graphics card and monitor support. Consult both device's documentation on what they support and try setting one that is applicable.
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  #3  
Old 23rd December 2007, 09:41 PM
mediator Offline
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I had fedora 5 earlier and on that 75 Hz was setup by default. I need the same configuration. Any hints or useful directions?
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  #4  
Old 23rd December 2007, 09:56 PM
lmo Offline
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What size do you want? 1024x768?

You can try to get a modeline from gtf and paste that in Section "Monitor".
Ex:
Code:
gtf 1024 768 75

  # 1024x768 @ 75.00 Hz (GTF) hsync: 60.15 kHz; pclk: 81.80 MHz
  Modeline "1024x768_75.00"  81.80  1024 1080 1192 1360  768 769 772 802  -HSync +Vsync
Then restart X by logging out and press CTRL+ALT+BACKSPACE.
See if you get an option for 75.

This can be a trial-and-error process and you may have to try gtf with many different frequencies to find the best one at the resolution you desire.

That is how I got it to let me have 1280x1024 when it couldn't figure it out itself.
Actually, my current favorite resolution is 832x624 for some reason, and it came up with that one by pure accident.
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  #5  
Old 23rd December 2007, 10:03 PM
mediator Offline
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I got this on using that command

Quote:
# 1024x768 @ 75.00 Hz (GTF) hsync: 60.15 kHz; pclk: 81.80 MHz
Modeline "1024x768_75.00" 81.80 1024 1080 1192 1360 768 769 772 802 -HSync +Vsync
I copied the Modeline part and pasted it exactly to the end of Monitor section. On restartng X, the screen didn't come up, showing me blank screen. I had to use one of the virtual terminals to get it back.. Now what to do??

Last edited by mediator; 23rd December 2007 at 10:11 PM.
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  #6  
Old 23rd December 2007, 10:11 PM
lmo Offline
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Paste it in xorg.conf like so (red):
Code:
# Xorg configuration created by system-config-display

Section "ServerLayout"
Identifier "single head configuration"
Screen 0 "Screen0" 0 0
InputDevice "Keyboard0" "CoreKeyboard"
EndSection

Section "InputDevice"
Identifier "Keyboard0"
Driver "kbd"
Option "XkbModel" "pc105"
Option "XkbLayout" "us+inet"
EndSection

Section "Monitor"
Identifier "Monitor0"
ModelName "Monitor 1024x768"
HorizSync 31.5 - 61.0
VertRefresh 50.0 - 75.0
Option "dpms"
Modeline "1024x768_75.00" 81.80 1024 1080 1192 1360 768 769 772 802 -HSync +Vsync
EndSection

Section "Device"
Identifier "Videocard0"
Driver "sis"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Videocard0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Viewport 0 0
Depth 24
Modes    "1024x768" "800x600" "640x480"
EndSubSection
EndSection

Last edited by lmo; 23rd December 2007 at 10:21 PM.
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  #7  
Old 23rd December 2007, 10:12 PM
mediator Offline
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Yea I did that (modified my previous post), but it showed me blank screen!! What to do?
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  #8  
Old 23rd December 2007, 10:15 PM
lmo Offline
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Oh, and make a backup copy or xorg.conf before working on it ... too late ... still do it.
Check that the location where you pasted it in is before the EndSection statement.
Check there are no typographical errors.
Comment it out by putting a # (pound sign) at the beginning of the line.

Mine also has a Modes statement. See blue editied in Post #6

Last edited by lmo; 23rd December 2007 at 10:23 PM.
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  #9  
Old 23rd December 2007, 10:26 PM
mediator Offline
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YEahehe, I always back up the default configuration before messing around. I had done exactly like u posted in codes. But it showed blank screen and flashing on/off light of the monitor. What next?


EDIT:

Quote:
Modes "1024x768" "800x600" "640x480"
I added this too, but it seems now it doesn't give any effect at all. The screen neither goes blank nor resolves. It remains at 60 Hz.

Last edited by mediator; 23rd December 2007 at 10:33 PM.
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  #10  
Old 23rd December 2007, 11:13 PM
lmo Offline
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What resoltion are you running in?
What resoluting choices are there?
How do you know that it is 60 Hz?
My monitor has a button to press that tells me what Hz it is in.
I think it is the V Hz that matters.

Quote:
flashing on/off light of the monitor
I think this means it went out of the monitor's range.
Then, like I said, the modelines is trial and error.
Try using gtf to get a modeline at, say, 65, and see if that one works ... and so on.

Last edited by lmo; 23rd December 2007 at 11:18 PM.
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  #11  
Old 24th December 2007, 12:58 AM
RJFUatHOME Offline
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One trick that I found works really nice is to play around with your VertRefresh line in the xorg.conf file.

I set mine at VertRefresh 50.0 - 76.0 to force all resolutions to 75 Hz even though on some rez's it can do better. Xorg reads my LCDs info correctly, but I get tossed out of range if it tries to follow what it says it can do, especially at lower resolutions.

edit: Thought I'd mention I like to also set the monitor to the appropirate Generic display setting when I play with xorg.conf so it doesn't try and "assume" what my model wants.

Last edited by RJFUatHOME; 24th December 2007 at 01:13 AM.
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  #12  
Old 24th December 2007, 02:30 AM
lmo Offline
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An alternate strategy is to comment out the HorizSync and VertRefresh lines to see what happens. Sometimes it works.
(Comment out the line by putting a # at the beginning of the line)
Or [desperately] try to force the VertReresh range up 65 - 75

I have had the best luck when the HorizSync and VertRefresh, e.g.,
Quote:
HorizSync 31.5 - 61.0
VertRefresh 50.0 - 75.0
were exactly correct for the specific monitor.
Please post the exact name and model number of your monitor so that a google search for it can prove that the numbers being used are correct. If they are not correct for the specific monitor, then all bets are off, and if it works that would only be by accident.
Also, tell what resolution you wish to use as the highest resolution. That can be a very important factor.
Also, what is the width and height of the screen in inches (use a ruler)? Measure the useable display portion on LCD's.

Last edited by lmo; 24th December 2007 at 02:36 AM.
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  #13  
Old 24th December 2007, 07:48 AM
mediator Offline
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@Imo : Thanx for ur help man. Today when I booted, it showed blank screen again. I looked at xorg and found [ Modes "1024x768" "800x600" "640x480" ] line to be missing for some strange reason that I added previously. So I added it again and now it works as before at 75 Hz. Thanx a lot for your help man!
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  #14  
Old 2nd January 2008, 08:26 AM
mediator Offline
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HI,
There's a new problem. It seems the monitor's window's overall size descreases on a refresh rate of greater than 60 Hz. On 60Hz it fills the screens correctly. But above, it shows much black screen beyond the windows edges. What can be the problem. Is it a hardware problem?
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  #15  
Old 2nd January 2008, 12:20 PM
pete_1967 Online
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Quote:
Originally Posted by mediator
HI,
There's a new problem. It seems the monitor's window's overall size descreases on a refresh rate of greater than 60 Hz. On 60Hz it fills the screens correctly. But above, it shows much black screen beyond the windows edges. What can be the problem. Is it a hardware problem?
There's no problem, that's what happens naturally with every monitor when referesh rate increases (and opposite when it decreases). You need to use your monitor's settings to re-adjust the screen size.
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