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I recently replaced the OSX on my Mac Mini with Ubuntu 16.04 LTS and I am having difficulty getting dual monitors working. Now, before someone points out "But this has already been answered... don't use Ubuntu 16.04 with Radeon graphics cards." I have a few specific questions that, if answered, might help others find their way through this process or a similar situation.

Here are the specs of my machine:

Mac Mini: Intel Core i7-2620M CPU@2.70 GHzx4 64-Bit 16GM memory

Here are the specs for the graphics cards

lspci -nn | grep -E 'VGA|Display'

00:02.0 Display controller [0380]: Intel Corporation 2nd Generation Core >Processor Family Integrated Graphics Controller [8086:0126] (rev 09)

01:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] >Whistler [Radeon HD 6630M/6650M/6750M/7670M/7690M] [1002:6741]

After installing Ubuntu 16.04 LTS it would boot to a blank purple splash screen and do nothing. So I poked around this forum and found the common solution(s) to adding nomodeset or radeon.modeset=0 to the line GRUB_CMDLINE_LINUX_DEFAULT="quiet splash radeon.modeset=0" in the etc/default/grub file and I was able to boot up and access the GUI, terminal, etc. with a single monitor.

My understanding from here is that adding nomodeset or radeon.modeset=0 to the grub file bypasses the kernel's default configuration to load DRM_RADEON_UMS, which is why this solves the booting issue.

Question 1: Is this correct? Is this what adding those options to the grub file is doing?

However, even after adding the radeon.modeset=0 option to grub, this

dmesg | egrep 'drm|radeon'

still reveals the following errors upon booting

[ 0.000000] Command line: BOOT_IMAGE=/boot/vmlinuz-4.8.0-36-generic.efi.signed >root=UUID=65510547-0bee-4725-9ded-efd3cbb5d1ed ro quiet splash radeon.modeset=0 >vt.handoff=7

[ 0.000000] Kernel command line: BOOT_IMAGE=/boot/vmlinuz-4.8.0-36->generic.efi.signed root=UUID=65510547-0bee-4725-9ded-efd3cbb5d1ed ro quiet splash >radeon.modeset=0 vt.handoff=7

[ 2.175464] [drm] Initialized drm 1.1.0 20060810

[ 2.215148] [drm:radeon_init [radeon]] ERROR No UMS support in radeon module! [ 14.899625] [drm:radeon_init [radeon]] ERROR No UMS support in radeon module

So I don't understand why I am still getting these UMS errors. Especially because if I type

lspci -k | grep -EA2 'VGA|3D'

then I get the following

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] >Whistler [Radeon HD 6630M/6650M/6750M/7670M/7690M]

Subsystem: Apple Inc. Whistler [Radeon HD 6630M/6650M/6750M/7670M/7690M]

Kernel modules: radeon

So it appears that the kernel is already loading the open source driver (here) that is compatible with my AMD Radeon Card according to this (it's a "Northern Islands" card).

So I'm not sure why I am getting UMS errors and why my dual monitors are not functioning. In fact, it appears that neither Intel's driver nor the radeon driver are being used because under system settings -> details -> overview I see

Graphics Gallium 0.4 on llvmpipe (LLVM 3.8, 256 bits)

and if I type

sudo lshw -c video

Then I get

*-display UNCLAIMED

description: VGA compatible controller

product: Whistler [Radeon HD 6630M/6650M/6750M/7670M/7690M]

vendor: Advanced Micro Devices, Inc. [AMD/ATI]

physical id: 0

bus info: pci@0000:01:00.0

version: 00

width: 64 bits

clock: 33MHz

capabilities: pm pciexpress msi vga_controller bus_master cap_list

configuration: latency=0

resources: memory:90000000-9fffffff memory:a8800000-a881ffff ioport:2000(size=256) memory:a8820000-a883ffff

*-display UNCLAIMED

description: Display controller

product: 2nd Generation Core Processor Family Integrated Graphics Controller

vendor: Intel Corporation

physical id: 2

bus info: pci@0000:00:02.0

version: 09

width: 64 bits

clock: 33MHz

capabilities: msi pm cap_list

configuration: latency=0

resources: memory:a8000000-a83fffff memory:a0000000-a7ffffff ioport:3000(size=64)

One of my monitor is displaying the GUI and terminal (functioning like normal) but it appears that NEITHER of my graphics controllers are being used.

Can someone help me figure out:

Question 2: Why are neither of my graphics controllers being used?

Question 3: How can I get them both to work and, hence, use dual monitors?

I would assume the Intel controller would be automatically used and the Radeon open source driver is being loaded by the kernel (I think) so I don't understand why they aren't both being used and why I don't have access to dual monitors.

Any help you could give me would be greatly appreciated. Thank you in advance for your help!

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