915resolution on Intel G33, Q33, and Q35 chipsets
Stuart Schmitt
 
06 April 2008


Introduction

The following instructions will help you get “unusual” screen resolutions to work in CentOS 5 on systems with recent Intel graphics adapters.  These instructions may apply to other systems that cannot be updated to use the latest Intel video drivers.

As of this writing, CentOS 5 is using an ancient version of the i810 video driver for X.Org.  The supplied (and updated!) driver does not support resolutions outside of the 4:3 aspect resolutions of traditional monitors.  If you have a new LCD widescreen monitor, the i810 driver will not allow you to use its native resolution.  There is a long-standing hack called 915resolution that makes “unusual” resolutions work, but the author has not updated it to work with the latest Intel chipsets (namely, G33, Q33, and Q35).  What follows is a modification that gets 915resolution to work with the new chipsets.  Indeed—this is a hack to a hack.


Instructions
  1. Download 915resolution 0.5.3 from the author’s website.

  2. Download this patch.  I lifted it from a Mandriva RPM [link].

  3. Open a shell and change to the directory where the downloads were saved.  Decompress the file:
    tar xzf 915resolution-0.5.3.tar.gz

  4. Apply the patch:
    patch 915resolution-0.5.3/915resolution.c 915resolution-newchipsets.patch

  5. Make and install 915resolution:
    cd 915resolution-0.5.3
    make
    make install

  6. Now you may use 915resolution.  To find a list of video modes, type
    915resolution -l
    Pick a mode you won’t ever use and assign it to your monitor’s native resolution.  I used 3a (1600×1200) and assigned it to 1440×900.  Hence my command was
    915resolution 3a 1440 900

  7. Edit /etc/X11/xorg.conf so that X.Org uses the appropriate resolution.  This setting goes in Section "Screen", SubSection "Display".  Add or edit the "Modes" line. Mine is
    Modes "1440x900"

  8. Close everything and log out.  X will restart; hopefully the changes have worked.

  9. As it is currently, the resolution setting will be lost on restart.  You need to add 915resolution to the startup scripts so that is works on restart.  Edit /etc/rc.d/rc.sysinit to run your 915resolution command right before RedHat Graphical Boot starts (so that RHGB uses the correct resolution).  Right before the line RHGB_STARTED=0 (at about line 350 on my system), insert the 915resolution command.  You must preface with the full path /usr/sbin/.  My new line 350 of rc.sysinit is
    /usr/sbin/915resolution 3a 1440 900

  10. Save and quit.  You are done.


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