I am attempting to run a desktop dual monitor setup on Xubuntu 16.04 as follows:

1 - Displayport (3840x2160) monitor connected to an AMD R9 390

2 - VGA (1280x1024) connected to integrated Intel HD 4600

If I enable the option "CPU Graphics Multi Monitor" in my BIOS and attempt to boot, I get a flashing underscore on the first monitor after splash screen. I can boot with only the AMD card enabled just fine.

I am using the latest xserver-xorg-video-amdgpu and xserver-xorg-video-intel drivers from this PPA.

My kernel version is: 4.7.8-040708-generic

What am I doing wrong?

  • Are you able to boot with only the integrated card fine? – Vardogor Mar 11 '17 at 4:29

Upgrading to a kernel version 4.9 and above may work; support for the newer AMDGPU driver in pre-GCN 1.2 AMD cards (which the R9 390 is) was added. The open source Oibaf or Padoka drivers may not support dual monitors with two different video cards.

Instructions for upgrading to 4.9 and compiling it for AMDGPU support can be found here.

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  • I successfully compiled 4.10.5, and have verified that I am using the amdgpu driver. lspci -nnk | grep -iA2 vga produces Kernel driver in use: amdgpu. Unfortunately, I am still getting the same result as before. – Gin Gon Mar 23 '17 at 7:58
  • @JinGon: Sorry for the extremely late reply. Are you able to boot from an Ubuntu (not Xubuntu) live disc and see if it works there? I've read that it's a limitation exclusive to Xubuntu, but it could be wrong. This is assuming, of course, that you haven't already fixed the problem in the time gap of my replying. – Vardogor Jun 9 '17 at 16:43

I have almost the same setup except it's an R9 FURY X outputting HD on one of the DisplayPorts and 4K (UHD) over HDMI. It was a nightmare getting it working well, but eventually, after trying many different tactics repeatedly over a couple months, I found the correct, AMDGPU-PRO drivers from AMD.

You'll probably want the current version, 16.60 for Ubuntu 16.04. I don't know how much they've improved the installation process since I first installed it a year ago, but I would recommend following their instructions. I had to install & reinstall an older version several times (and tweak some X settings) before it would work correctly all the time.

I don't use the integrated video (Intel), but I have had it working simultaneously with the other two screens. Really though, the 2 large displays offer quite enough screen real estate for me.

Good luck.

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  • @Vardoger's link says you must update to a newer kernel, but using AMD's pro drivers, I didn't need to update it. I'm still running 4.4.0 (after many headaches trying to get the opensource stack working). As suggested, I did need to blacklist the radeon and modesetting drivers, but I think the installer does that for you these days. – destenson Mar 13 '17 at 0:31

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