# Adjust LCD Refresh Rate [SOLVED]

## bergs

Hi

My Dell Ultrasharp 1901FP 19" runs at 1280x1024 @ 75 Hz. With these settings, sometimes I get pixel errors (pink pixels, mostly when viewing a dark picture). I don't know if this is monitor or graphics card related (ATI 9700). Anyway, I've got the same problem with Windows XP. I found out that reducing the refresh rate to 60 Hz solves it.

Now, how can I do that with X? I used fglrxconfig to create the XF86Config. All modelines are commented (?). The monitor section looks like:

Section "Monitor"

    Identifier  "Monitor0"

    HorizSync   30-80

    VertRefresh 60              # old settings: 56-76

    Option "DPMS"

What can I do?

SimonLast edited by bergs on Wed Jul 21, 2004 8:41 am; edited 2 times in total

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## 'nux_Tau

Sometimes, bad pixels are just inherent to the hardware. They are hard to detect on a screen with various elements or colors, but they are often there. The configuration information seems fine, I suggest you check the onscreen menu for your monitor to see what vertical/ horizontal refresh rates and resolution it is running at, make sure that is within the permissable range, and put that in your post.

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## Safrax

LCD's should be run at 60hz and only 60hz.  They don't refresh like normal CRT's do, only changed pixels actually well "refresh" (change is more acurate though).

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## 'nux_Tau

He's a guru for a reason, I suppose.   :Very Happy: 

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## hammer_jv

THanks for the tip..

The monitor tells you that it should be run at 60 but i can't figure out how to force that in my XF86Config-4,  Mine has similar symptoms except i can see it all the time.  And it won't line up right even using the adjustments on the monitor i have them maxed and i still have a half inch of black at the top of the screen.

Any help would be appreciated

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## bergs

Sorry, I almost forgot this post ...

My monitor has these specs:

Horizontal scan range: 30 kHz-80 kHz (automatic)

Vertical Scan Range: 56 Hz-76 Hz (automatic)

However, setting the option VertRefresh 60 in xorg.conf (as shown in my first post) has no effect. Any ideas?

Rigth now I'm not at my home computer, so I can't check if the on-screen menu let me change scan range settings. But I doubt it, since these are detected automatic.

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## bergs

I just checked the monitor and there is NO on-screen option to set the refresh rate.

Anyone?  :Crying or Very sad: 

Simon

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## nekranos

A bump for this topic. I have the same model (1901FP), and can't figure out how to get xorg to use 60Hz instead of 75Hz. Same problem as the original poster. "bergs": did you ever figure out how to fix this?

Oddly enough, in the console, any resolution that is supported by the LCD runs at 60Hz (which is good). Feeding X any resolution except for 640x480 forces it into 75Hz.

I tried setting [Option "IgnoreEDID" "True"] in the "Device" section, which made it run at 60Hz; but it would only let me use 640x480.

I can't figure out what's wrong at this point, and I'm tempted to go use WinXP (which I know does 1280x1024@60Hz fine)....

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## bergs

Try adding this modeline to your xorg.conf

Modeline "1280x1024@60" 114.98 1280 1312 1744 1776 1024 1045 1055 1076

It works for me.

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## nekranos

I tried appending that line into the monitor section of xorg.conf, and it somewhat works - it runs at 60Hz. However...

The screen appears distorted for some reason. Black bars to the top and sides, screen not full. Did you run into this problem at all, and if so, how did you fix it?

I really hate this radeon mobility + external lcd setup right now....

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## allucid

 *Safrax wrote:*   

> LCD's should be run at 60hz and only 60hz.

 

I have to disagree. Most newer LCD's are capable of running at >60hz and do so quite well. Mine is currently running at ~76. Run at whatever speed the LCD is made to run at. I believe you can omit the monitor secition in your XF86Config and X will detect the correct resolution/refresh rate for your LCD.

Disclaimer: I take no responsiblity if you burn out your LCD.  :Wink: 

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## bergs

Sorry, can't help you. I did not run into that problem.

Simon

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