Fedora Linux

xorg.conf :

Section 'Device'
 Identifier 'Card0'
 Driver 'radeon'
 VendorName 'ATI'
 BoardName 'ATI 7500'
 BusID 'PCI:1:0:0'
 Option 'MergedFB' 'on'
 Option 'CRT2HSync' '31.0 - 80.0'
 Option 'CRT2VRefresh' '50.0 - 75.0'
 Option 'MergedXinerama' 'on'
 Option 'MetaModes' '800x600-1024x768'
 Option 'CRT2Position' 'RightOf'
EndSection

The MergedFB option enables dual video output. CRT2HSync and CRT2VRefresh set the horizontal and vertical frequency ranges for the second monitor (the settings for the primary monitor are in the Monitor section of the file), and the MetaModes option sets the resolution of the two displays. MergedXinerama enables sending display hints to applications, and CRT2Position sets the the position of the second display relative to the first for the purpose of mouse movement and window positioning (possible values are Above , Below , LeftOf , or RightOf ).

Restart the X server by changing to runlevel 3 and then back to 5, by restarting the system, or by terminating the running X server with Ctrl-Alt-Backspace (save your work first!). When the X server restarts, both displays should be active.

3.4.1.3. Configuring dual video on an ATI video card using the ATI closed source driver

The ATI closed source driver is configured in much the same way as the other drivers. First, configure and test your system using the ATI closed source driver fglrx , and then add the lines highlighted in bold to the Device section of your /etc/X11/xorg.conf :

Section 'Device'
 Identifier 'Card0'
 Driver 'fglrx'
 VendorName 'ATI'
 BoardName 'ATI 7500'
 BusID 'PCI:1:0:0'
 Option 'DesktopSetup' '0x00000200'
 Option 'HSync2' '31.0 - 80.0'
 Option 'VRefresh2' '50.0 - 75.0'
EndSection

The DesktopSetup option enables dual video output and specifies that the monitor attached to connector 1 is on the left; change this value to '0x00000201' if the monitors are reversed (it's not always apparent whether the internal or external monitor is attached to connector 1). HSync2 and VRefresh2 set the horizontal and vertical frequency ranges for the second monitor (the settings for the primary monitor are in the Monitor section of the file). The resolutions will automatically be selected from available options by the device driver.

Restart the X server by changing to runlevel 3 and then back to 5, by restarting the system, or by terminating the running X server with Ctrl-Alt-Backspace (save your work first!). When the X server restarts, the two monitors should display two halves of the desktop.

3.4.2. How Does It Work?

The X server contains code to manage two (or more) separate video cards, combining them into a single desktop. However, the X.org server and the configuration file layout were never really designed for multiple outputs from one card controlled by one driver; for example, there is no way to associate more than one Monitor section in the configuration file with a single Device (video card) section.

Some video card drivers have been enhanced to support multiple video outputs, and in order to fit within the X.org configuration file format, the configuration information for the second monitor is placed in the Device section.

There are two ways to use multiple monitors as part of a single display in X:

? Each monitor can be given a distinct Screen number, which enables output to be sent to a specific monitor but prevents windows from spanning displays or being moved from one display to another.

? Use Xinerama, which is named after the old Cinerama movie technology and that combines multiple monitors into a single large display, permitting windows to span monitors and to be moved between monitors.

All of the X.org video card drivers that support multiple video outputs use the Xinerama approach, but the Xinerama extensions used to inform applications of the underlying monitor geometry may be enabled or disabled using configuration options (with the exception of the ATI driver, which does not offer this capability). This information is particularly useful to window managers because it enables the window manager to correctly center dialogs in the middle of the monitor instead of the middle of the virtual desktop, and to make maximized windows fill a monitor instead of spanning monitors.

3.4.3. What About...

3.4.3.1. ...using dual video output with another video driver?

Very few of the other X.org video drivers support multiple video outputs. If you have another driver and want to see the options supported, look for a manpage for your driver. For example, to see the driver options for the Intel 810 adapter:

$ man i810

3.4.4. Where Can I Learn More?

? The manpages for the radeon driver