How do I determined, whether Xorg is using Xinerama, DDC and Reduced Blanking ??

Just adding few options in Xorg.conf is sufficient ?

If I have to check from command-line, then how can I check above mentioned settings ?

(I am using VIA chipset and Dell DELA07A monitor, Just in case this info required )


If I execute the command: Xorg -extension ? It gives me the output as

[mi] Extension "?" is not recognized
[mi] Only the following extensions can be run-time disabled:
[mi]    Generic Events
[mi]    Composite
[mi]    DAMAGE
[mi]    DPMS
[mi]    GLX
[mi]    MIT-SHM
[mi]    RANDR
[mi]    RENDER
[mi]    SECURITY
[mi]    X-Resource
[mi]    XFIXES
[mi]    XINERAMA
[mi]    SELinux
[mi]    XTEST
[mi]    XVideo

As per the above output, I assume that it is possible to enable/disable extensions in runtime. Question is HOW ? If it is really possible then I can enable/disable the XINERAMA extension as and when I want

I also assume that when XINERAMA is ON in dual-head then maximizing an open application will span on both monitor. And when XINERAMA is off then maximizing an application will span to one monitor only. ( Correct me if I'm wrong )

  • cat /var/log/Xorg.0.log (for display :0). See also xdpyinfo for some information. Nov 1, 2013 at 13:10
  • xdpyinfo | egrep -i 'Xinerama|DDC|Reduced Blanking' returns XINERAMA here. Nov 1, 2013 at 19:13

1 Answer 1


To check if Xinerama is enabled:

xdpyinfo| grep XINERAMA

To get the settings of Xinerama extension:

xdpyinfo -ext XINERAMA

About reduced blanking: you can show the modes the Xserver knows about by calling xrandr --verbose and examining the current one. Using the cvt tool you can generate modelines with/without reduced blanking for your desired resolution and compare those to the ones you see in xrandr output.

DDC information: I am not really sure. Maybe have a look at the X log file. With the mentioned xrandr --verbose you can also see the EDID of connected monitors.

Update: I just found https://wiki.ubuntu.com/X/Troubleshooting/Resolution where a tool called ddcprobe is mentioned. So - without knowing it - I want to add that to the list.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .