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There are lots of questions on this but I've read them all and none helped me!

  • ATI Radeon HD 5400 Series

  • PCI Express 2.0

My co-worker attempted to use 3 displays on windows, that failed...

However he managed to get 3 displays on ubuntu using the exact same graphics card as me!

I know its possible!

  • Display One: 22" DVI

  • Display Two: 22" VGA

  • Display Three: 19" VGA

My graphics card has: HDMI, DVI, VGA.

  • The HDMI goes to Display One using a HDMI to DVI converter

  • The VGA goes to Display Two directly

  • The DVI goes to Display Three using a DVI to VGA converter

When I open ubuntu display settings, i see the 3 displays, however Display Three is set to OFF by default... When i try to enable it, my PC does nothing!

When I open Catalyst Control Center, i see the 3 displays again, but the 3rd is set to "disabled" and I cannot enable it...

What do i need to do?

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3 Answers 3

Before we start, sometimes the HDMI port is pushed by the same hardware that pushes DVI/VGA so it might be that you need three 'real' ports not a port that works if and only if the other is disabled.

To find out if the previous is the case, disable your second monitor and see if the HDMI is enable-able then. If it is, then it's the case. If it still isn't then keep reading...

Mine is 2 DVIs and a displaylink port.

I currently have this working without 3D support using Xinerama like this:
xorg.conf

Section "ServerLayout"
    Identifier     "aticonfig Layout"
    Screen      0  "aticonfig-Screen[0]-0" 0 0
    Screen         "aticonfig-Screen[0]-1" LeftOf "aticonfig-Screen[0]-0"
    Screen         "aticonfig-Screen[0]-2" LeftOf "aticonfig-Screen[0]-1"
EndSection

Section "Module"
EndSection

Section "ServerFlags"
    Option      "Xinerama" "on"
EndSection

Section "Extensions"
    Option      "Composite" "Enable"
EndSection

Section "Monitor"
    Identifier   "aticonfig-Monitor[0]-0"
    Option      "VendorName" "ATI Proprietary Driver"
    Option      "ModelName" "Generic Autodetecting Monitor"
    Option      "DPMS" "true"
EndSection

Section "Monitor"
    Identifier   "aticonfig-Monitor[0]-1"
    Option      "VendorName" "ATI Proprietary Driver"
    Option      "ModelName" "Generic Autodetecting Monitor"
    Option      "DPMS" "true"
EndSection

Section "Monitor"
    Identifier   "aticonfig-Monitor[0]-2"
    Option      "VendorName" "ATI Proprietary Driver"
    Option      "ModelName" "Generic Autodetecting Monitor"
    Option      "DPMS" "true"
EndSection

Section "Device"
    Identifier  "aticonfig-Device[0]-0"
    Driver      "fglrx"
    BusID       "PCI:1:0:0"
    Screen      0
EndSection

Section "Device"
    Identifier  "aticonfig-Device[0]-1"
    Driver      "fglrx"
    BusID       "PCI:1:0:0"
    Screen      1
EndSection

Section "Device"
    Identifier  "aticonfig-Device[0]-2"
    Driver      "fglrx"
    BusID       "PCI:1:0:0"
    Screen      2
EndSection

Section "Screen"
    Identifier "aticonfig-Screen[0]-0"
    Device     "aticonfig-Device[0]-0"
    Monitor    "aticonfig-Monitor[0]-0"
    DefaultDepth     24
    SubSection "Display"
        Viewport   0 0
        Depth     24
                Modes "1440x900_60.00"
    EndSubSection
EndSection

Section "Screen"
    Identifier "aticonfig-Screen[0]-1"
    Device     "aticonfig-Device[0]-1"
    Monitor    "aticonfig-Monitor[0]-1"
    DefaultDepth     24
    SubSection "Display"
        Viewport   0 0
        Depth     24
                Modes "1440x900_60.00"
    EndSubSection
EndSection

Section "Screen"
    Identifier "aticonfig-Screen[0]-2"
    Device     "aticonfig-Device[0]-2"
    Monitor    "aticonfig-Monitor[0]-2"
    DefaultDepth     24
    SubSection "Display"
        Viewport   0 0
        Depth     24
                Modes "1440x900_60.00"
    EndSubSection
EndSection

with binary driver...

Where is xorg.conf: /etc/X11/xorg.conf
What is xorg.conf: It's a way to tell your computer 'No do not auto configure...I know better. Do it like this:'

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What is xorg.conf and where can i find it? –  AlexMorley-Finch Mar 22 '12 at 13:16
    
/etc/X11/xorg.conf Good practice to make backups before editing :D –  earthmeLon May 23 '12 at 2:40
    
would you mind adding comments to the code to indicate the DisplayLink settings? i'm having this problem unix.stackexchange.com/questions/89585/… thank you very much in advance! –  user128334 Sep 5 '13 at 21:24

I know this is an old question, but I have exactly the same setup as you, and have been running into the same problem. I figured I'd share this here, since it hasn't been discussed anywhere else.

The problem seems to be the proprietary AMD driver in combination with certain older GPUs, rather than any particular X settings. Since these cards only use two pixel clocks, I suspect some combination of lazy coders and stingy testers blocked the use of three displays in their driver, rather than build a workaround to allow the sharing of two pixel clocks among three displays.

A simple fix for you is to open the command line and run:

sudo apt-get remove --purge fglrx*

This removes the AMD driver, along with Catalyst Control Center, and forces Ubuntu to use the Linux Radeon driver instead. You should still be able to configure the display settings using the Ubuntu display manager, instead of fiddling with xorg.conf.

Although the open-source driver lets you use three displays, you will need to set at least two of your monitors to the same resolution and refresh rate (there's no possible way to get around this: different resolution/refresh rate=different pixel clock speed). Unfortunately, I've had problems with any setup other than all three matching. This limits you to the settings available on your lowest-resolution display. You also lose out on any 3D acceleration features provided by the AMD driver.

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Even though this is a few years old, I see there is no accepted answer. I have a Sapphire Radeon HD 5450 card that drives three monitors. My monitors are VGA 1440x900, HDMI 1680x1050, and VGA 1440x900. The ports are VGA, HDMI, and DVI. Therefore, for the DVI port I use an adapter. You would need to use the open source xorg drivers for best results. No xorg.conf was necessary. In Xubuntu I had to fiddle in Monitor Preferences a bit, but it works great. Each monitor is at its native resolution. In Xubuntu in Monitor Preferences, I disabled all monitors but the far left one. Then I configured the far left how I wanted it. Then I enabled the middle monitor and configured it. Then I enabled the far right one and configured it. You will need to set the card as primary in BIOS. This only worked for me in 14.04, not 12.04. Linux Mint 17 also works with this.

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