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I have gone through installing versions 14, 15 and 16. However, none of the versions seem to solve the issue of getting my 2nd monitor to display. When I go to additional drivers I only have an option selected for *Using processor microcode firmware for Intel CPU's from Intel microcode (proprietary).

My second monitor appears as "Unknown device" in the display application. I've tried the other Q/A posted with no luck including purging and updating drivers. I am using a AMD/ATI RV730XT [Radeon HD 4670] Graphics card. Monitor is connected through VGA and DVI port. An interesting thing is when my computer boots up, the Bios and Grub display using both monitors. It isn't until Ubuntu boots that my second monitor turns off. If I disconnected one monitor the other monitor will turn on so I know it can see the other device and use it.

The dual monitors worked for all versions of Windows, but I really don't want to use Windows anymore. I'm open to even buying a different graphics card if that is what I need to do. Will someone please help? Thanks in advance.

--Update to Question-- Okay, so guessing my graphics card just isn't supported for dual monitors in Ubuntu 16.xx. I'm currently using [Radeon HD 4670]. Can someone tell me what graphics cards ARE supported in Ubuntu 16.xx (DUAL MONITOR ONLY)? Has anyone actually got dual monitors working???

  • Have you configured the second monitor to work in Ubuntu? Go to Settings, Display, and check if the second monitor is recognised. If so, you need to enable it within the same menu. AFAIK second screens don't work by just plugging it. – user308164 Dec 1 '16 at 14:10
  • My external monitor could be successfully recognized after I upgrade from 16.04 to 18.04. – Xuan Luo Sep 11 '18 at 23:23
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FIXED - I wanted to share the solution just in case anyone else goes through the nightmare I went through in order to get dual monitors working on 16.04 or 16.10. I spent the better part of a weekend and my week outside of work on this...

I have an on-board video card (not used) + AMD/ATI RV730XT [Radeon HD 4670] with DVI/VGA connectors to 2 - Dell 23" monitors.

1.) Go to additional drivers and select "Do not use the device" for "Unknown: unknown". 2.) Open display application, if you are like me you will see 2 boxes. One that says "Dell 23" and another that says "Unknown display". 3.) Click "Dell 23" box. Now a third box will magically appear and you will be left with 3 boxes total that say "Dell 23", "Dell 23", and "Unknown display". 4.) Click the "Dell 23" that does not contain the launcher placement and turn this monitor off. 5.) Now enable the "Unknown: unknown" display. 6.) Click apply and the 2nd monitor will turn on magically. Whew!

I'm not sure there is any logic whatsoever in this process, but it ended up fixing my issue and I now have dual monitors working in Ubuntu.

  • Seems like a bug on your end, when I do this then at step 3 I don't get a third box that represents a display (but my primary screen is also not named 'unknown' but 'built-in display').. – poepje Jul 11 '17 at 13:14
  • For me, I just opened the "Displays" application and turned the second monitor back on. For some reason. it suddenly went off on its own. – Tasos Anesiadis Nov 20 '17 at 1:33
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I don't think that ubuntu would focus on Dual monitor for supporting the graphic cards. however I can see that there are lists on what graphic cards are supported.

https://wiki.ubuntu.com/HardwareSupportComponentsVideoCards

Your question seems to be related to : Ubuntu 16.04 Dual monitor doesn't work after booting

Take a look at this too : http://www.omgubuntu.co.uk/2016/03/ubuntu-drops-amd-catalyst-fglrx-driver-16-04

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