Page 1 of 3 123 LastLast
Results 1 to 10 of 27

Thread: HOWTO: Wrong/Low Resolution and flicker

  1. #1
    Join Date
    Sep 2006
    Beans
    1,610
    Distro
    Ubuntu 9.10 Karmic Koala

    Post HOWTO: Wrong/Low Resolution and flicker

    The Xorg server - the code that provides a graphic display - is very good about determining what an attached monitor can do. There are limitations.

    This HOWTO explains one process for obtaining a rock-solid graphics screen within the constraints of your hardware's abilities. There are many other ways to do this.

    Overview of the problem:
    When Xorg starts, it tries to figure out what kind of monitor you have via DDC/CI and EDID protocols. If your monitor and cabling are first-rate, you will never need to care about any of this. (Yay!)

    If not, Xorg will pick a "safe" VESA resolution and use that: probably not at all what you expected, and not likely to be satisfactory. (Grr.)

    Lucky for us all, Xorg is highly configurable and it's very easy to get the exact resolution(s) that you want, deserve, and yes, paid-for with your invested time.

    Warning: If you are terrified by a Linux command line, at least TRY to follow this procedure. It won't hurt you and it will help.

    Still with me? Then let's proceed:


    Step #1: What kind of monitor do you have? What are its capabilities? What is its maximum resolution?

    Virtually every monitor vendor will publish the specifications for their products on the web. You can find them if you just look but first, you'll need the Vendor Name and Model of that monitor. It will be printed on a plate or tag, glued, screwed, or riveted to the back, top, bottom, or side of your monitor. Go look for it now. Write that information down and keep it handy.

    Step #2: Fetch your specs.

    Bring up a browser window and search for that model eg, 'dell 3007wfphc'.

    Look for any site with details and specifications; the vendor's site is best, but most review sites will provide specifications too.

    Ideally, you will find the "Horizontal Sync" range, expressed in kilohertz (KHz or khz), and the "Vertical Refresh" range, expressed in hertz (Hz).

    If you found that, write it down like:
    Code:
    HorizSync 49.31 - 98.71
    VertRefresh 60
    and proceed to Step #4.

    If not, then look for the "Maximum Resolution". This will be listed as something like "2560 x 1600 at 60Hz". Write that down.

    Step #3: Calculate the frequencies from the specified resolution.

    Open a terminal window (Applications -> Accessories -> Terminal) and enter
    Code:
    cvt 2560 1600 60
    Hit Enter. This will output the following
    Code:
    # 2560x1600 59.99 Hz (CVT 4.10MA) hsync: 99.46 kHz; pclk: 348.50 MHz
    Modeline "2560x1600_60.00"  348.50  2560 2760 3032 3504  1600 1603 1609 1658 -hsync +vsync
    Aha! The vertical refresh will be exactly 59.99Hz and the horizontal sync will be 99.46KHz. Write it down as:

    Code:
    HorizSync 99.46
    VertRefresh 59.99

    Step #4: Create a basic xorg.conf

    Write the following commands down on paper because we're going to turn off the GUI and run a few commands from the console.

    Flip to the text console via Ctrl+Alt+F1 and log in.

    Execute these commands:
    Code:
    sudo /etc/init.d/gdm stop
    sudo X -configure
    sudo /etc/init.d/gdm start ; exit
    (ignore any notices about the "new" way of starting/stopping services - those "new" ways work, and so does this way, but this way works on all releases)

    You're back at the GUI login screen, so log in and bring up the rest of these directions.

    Step #5: Edit the basic configuration.

    Edit the new configuration by opening a terminal window and running the following command:
    Code:
    sudo gedit xorg.conf.new
    Scroll down to the entry
    Code:
    Section "Monitor"
            Identifier   "Monitor0"
            VendorName   "Monitor Vendor"
            ModelName    "Monitor Model"
    EndSection
    Add lines after the Identifier label to include the values you found (or calculated). The entry for that Dell monitor will look like:
    Code:
    Section "Monitor"
            Identifier   "Monitor0"
            HorizSync    49.31 - 98.71
            VertRefresh  60.0
            VendorName   "Monitor Vendor"
            ModelName    "Monitor Model"
    EndSection
    Note: If you appreciate details, fill in the VendorName and ModelName values (within quotes) like
    Code:
    Section "Monitor"
            Identifier   "Monitor0"
            HorizSync    49.31 - 98.71
            VertRefresh  60.0
            VendorName   "Dell"
            ModelName    "3007WFP-HC"
    EndSection

    Step #6: Save the new configuration.

    Save that file. Then click File -> Save As (in gedit) and save the file as /etc/X11/xorg.conf then exit gedit.

    Now, you have a new Xorg configuration installed where Xorg can see it, and you have a backup in your home folder.
    Step #7: Restart X and test.

    In the terminal window, enter
    Code:
    sudo /etc/init.d/gdm restart
    You'll be logged off and the login screen should appear a few seconds later at full resolution. Congratulations, you have just done what your graphics card tried to do, but failed.

    ------

    YIKES: If the screen goes black and stays that way, then you have either not provided the correct information for your monitor or your graphics card cannot run that monitor at these frequencies. Here's how you get back to low-res graphics mode:

    Flip to the console via Ctrl+Alt+F1 and log in. Run these commands:
    Code:
    sudo rm -f /etc/X11/xorg.conf
    sudo /etc/init.d/gdm restart ; exit
    Now you can start over from Step #1, and find YOUR monitor's specifications. If you're very sure you have the correct numbers, then it is possible that your graphics card can't operate at the required frequencies. Replace it.

    --

    For further information on xorg.conf, bring up a terminal window and run
    Code:
    man xorg.conf
    For further information on the Xorg server, bring up a terminal window and run
    Code:
    man X
    Comments are always welcome.
    Last edited by Giblet5; November 12th, 2009 at 07:23 PM. Reason: look! that rabbit can type!
    sı ɯǝ1qoɹd ɹnoʎ ʇɐɥʍ ǝǝs ı ʞuıɥʇ ı

  2. #2
    Join Date
    Apr 2009
    Beans
    56

    Re: HOWTO: Wrong/Low Resolution and flicker

    THanks for the excellent guide With its help I am able to configure my screen resolution in ubuntu 9.10 satisfactorily.

  3. #3
    Join Date
    Mar 2007
    Location
    Portsmouth, UK
    Beans
    Hidden!
    Distro
    Ubuntu 11.10 Oneiric Ocelot

    Re: HOWTO: Wrong/Low Resolution and flicker

    Excellent guide, Giblet5.

  4. #4
    Join Date
    Apr 2006
    Beans
    5

    Re: HOWTO: Wrong/Low Resolution and flicker

    I followed you very easy guide and when i was done and restarted i had a problem. The screen was flickering and my keyboard when i typed was all out of whack. what did i do wrong. i am gunna try to reinstall again and try once more. Any answers would be grand. Thanks.

    NVM. I realized that i had inverted the variables. I put the horizontal for the vertical. it doesn't seem to like that apparently. Thanks for your amazing guide again.
    Last edited by dracoalutusvulpes; November 29th, 2009 at 04:38 AM.

  5. #5
    Join Date
    Jun 2009
    Beans
    15

    Re: HOWTO: Wrong/Low Resolution and flicker

    Help! When I used the first command in step 4, my computer went into a full screen terminal with black background that I can't get out of and when I did the gedit command in step 5 it gives me a warning cannot open display. Please help!

  6. #6
    Join Date
    Nov 2009
    Beans
    2

    Smile Re: HOWTO: Wrong/Low Resolution and flicker

    Thanks... Newbie here!!! Works fine for me... I have a sis mirage 3 graphics card ang it works fine...
    Excellent..., Giblet5

  7. #7
    Join Date
    Dec 2009
    Beans
    40
    Distro
    Ubuntu Gnome 13.10 Saucy Salamander

    Re: HOWTO: Wrong/Low Resolution and flicker

    I tried this, but knowing me, I probably messed something up. I have a Dell E773c monitor, the specs of which are located here: http://support.dell.com/support/edoc...Specifications.
    I entered this:
    Section "Monitor"
    Identifier "Monitor0"
    HorizSync 67.68
    VertRefresh 74.79
    VendorName "Dell"
    ModelName "E773c"
    EndSectionI did not know how to find the range for HorizSync that you did, so I just ran
    cvt 1154 864 75 and used those numbers. When I try to restart the GUI, a message pops up that says:
    (EE) open /dev/fb0: No such file or directory exists.
    (EE) Screen(s) found, but none have a usable configuration.

    I'm not sure what I did wrong. Can you help? Thanks in advance.

  8. #8
    Join Date
    Dec 2009
    Beans
    40
    Distro
    Ubuntu Gnome 13.10 Saucy Salamander

    Re: HOWTO: Wrong/Low Resolution and flicker

    Help! When I used the first command in step 4, my computer went into a full screen terminal with black background that I can't get out of and when I did the gedit command in step 5 it gives me a warning cannot open display. Please help!
    The black screen is supposed to come up. You have to run the rest of the commands in Step #4 before moving onto Step #5. Alternatively, you can run:
    sudo /etc/init.d/gdm stop
    Then, after the black screen comes up, run
    sudo X -configure
    Now do Step #5, but change gedit to nano. After you save xorg.conf.new, run
    cp /home/elijah/xorg.cong.new /etc/X11/xorg.conf
    Now do Step #7 and this should work.

  9. #9
    Join Date
    Dec 2009
    Beans
    1

    Re: HOWTO: Wrong/Low Resolution and flicker

    Thank yo so much Giblet5!

    I had tried so many things to solve my problem. Then I read your post & followed your instructions.

    Godbless!

  10. #10
    Join Date
    Jan 2005
    Location
    Argentina
    Beans
    39
    Distro
    Ubuntu

    Re: HOWTO: Wrong/Low Resolution and flicker

    Thanks for the guide, but it is not working for me.

    The first thing is that if i go by my monitor specifications, it says:

    Synchronization
    Resolution: 2048 X 1152@60Hz
    Horizontal: 30 ~ 75 kHz
    Vertical: 56 ~ 61 Hz

    if i do the cvt i get:

    ~$ cvt 2048 1152
    # 2048x1152 59.90 Hz (CVT 2.36M9) hsync: 71.58 kHz; pclk: 197.00 MHz
    Modeline "2048x1152_60.00" 197.00 2048 2184 2400 2752 1152 1155 1160 1195 -hsync +vsync

    Horizontal 71.49
    Vertical 59.83

    Anyway, no matter what i try:

    Section "Monitor"
    Identifier "Monitor0"
    HorizSync 30-75
    VertRefresh 61.0
    VendorName "Samsung"
    ModelName "2343nwx"
    EndSection

    OR

    Section "Monitor"
    Identifier "Monitor0"
    HorizSync 71.49
    VertRefresh 59.83
    VendorName "Samsung"
    ModelName "2343nwx"
    EndSection

    I only get 1024x768, or a black screen.

    Any ideas/help?

Page 1 of 3 123 LastLast

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •