I'm trying to set up a triple monitor desktop at my office using Fedora 17, but it seems impossible, let me explain the setting:

• Laptop ASUS K53SD with 2 graphic cards, Intel and nVidia (Screen controled by Intel card)
• 24" Full HD monitor connected to the HDMI output (controlled by Intel card)
• 23" Full HD monitor connected to an USB-HDMI adapter (via framebuffer in /dev/fb2, apparently)
• VGA output (not used) controlled by nVidia card

First of all, the USB-HDMI adapter works perfectly, it gives me a green screen (which means the communication is OK) and I can make it work if I set up a single monitor setting via framebuffer in Xorg. Here I leave the page where I got the instructions: http://plugable.com/2011/12/23/usb-graphics-and-linux

Now I'm trying to set up the the two main monitors (laptop and 24") with the intel driver and the 23" with the framebuffer, but the most succesful configuration I get is the two main monitors working and the third disconnected.

Do you have any idea what can I do to make this work?

Here I leave my xRandr output and my Xorg conf:

-> xrandr
Screen 0: minimum 320 x 200, current 3286 x 1080, maximum 8192 x 8192
LVDS1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
   1366x768       60.0*+
   1024x768       60.0  
   800x600        60.3     56.2  
   640x480        59.9  
VGA2 disconnected (normal left inverted right x axis y axis)
HDMI1 connected 1920x1080+1366+0 (normal left inverted right x axis y axis) 531mm x 299mm
   1920x1080      60.0*+   50.0     25.0     30.0  
   1680x1050      59.9  
   1680x945       60.0  
   1400x1050      74.9     59.9  
   1600x900       60.0  
   1280x1024      75.0     60.0  
   1440x900       75.0     59.9  
   1280x960       60.0  
   1366x768       60.0  
   1360x768       60.0  
   1280x800       74.9     59.9  
   1152x864       75.0  
   1280x768       74.9     60.0  
   1280x720       50.0     60.0  
   1440x576       25.0  
   1024x768       75.1     70.1     60.0  
   1440x480       30.0  
   1024x576       60.0  
   832x624        74.6  
   800x600        72.2     75.0     60.3     56.2  
   720x576        50.0  
   848x480        60.0  
   720x480        59.9  
   640x480        72.8     75.0     66.7     60.0     59.9  
   720x400        70.1  
DP1 disconnected (normal left inverted right x axis y axis)
   1920x1080_60.00   60.0  

The Xorg file:

# Xorg configuration file for using a tri-head display

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "HDMI" 0 0
    Screen      1  "USB" RightOf "HDMI"
    Option         "Xinerama" "on"
EndSection

########### MONITORS ################

Section "Monitor"
    Identifier     "USB1"
    VendorName     "Unknown"
    ModelName      "Acer 24as"
    Option         "DPMS"
EndSection

Section "Monitor"
    Identifier     "HDMI1"
    VendorName     "Unknown"
    ModelName      "Acer 23SH"
    Option         "DPMS"
EndSection

########### DEVICES ##################

Section "Device"
    Identifier     "Device 0"
    Driver         "intel"
    BoardName      "GeForce"
    BusID          "PCI:0:02:0"
    Screen          0
EndSection

Section "Device" 
    Identifier     "USB Device 0" 
    driver         "fbdev" 
    Option         "fbdev" "/dev/fb2" 
    Option         "ShadowFB" "off"
EndSection 


############## SCREENS ######################

Section "Screen"
    Identifier     "HDMI"
    Device         "Device 0"
    Monitor        "HDMI1"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "USB"
    Device         "USB Device 0"
    Monitor        "USB1"
    DefaultDepth    24
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection