Using 2 monitors with 2 discrete GPUs (Radeon RX 580 + HD 4850)

Rynak · 2019-06-21 18:54:05

Hi all,

I recently got a new GPU (RX580) that I want to use to play games on Linux. I want to use the 2nd GPU as well because I can connect the 2nd monitor (DVI) only to the 2nd GPU. So my setup is:

RX 580 (DP, HDMI, DVI)
|
|-- Monitor 1 (DP) "Acer"

HD 4850 (DVI, HDMI, DP)
|
|-- Monitor 1 (HDMI) "Acer"
|
|-- Monitor 2 (DVI) "Medion"

When I start X without configuration, xrandr shows me 2 providers and (using arandr) I can enable one output on each one: DP on RX580 and HDMI on HD4850. I cannot enable the DVI output on the old GPU, which is exactly what I want. I also tried using the config below but then xrandr didn't even show the 2nd GPU (just 1 provider, RX580 with DP).
When I write a config with only the HD4850, I can use both outputs of the old GPU but then I am not using the RX580 of course.

The xorg log for no config file, the config file below. Especially the line

(WW) VGA arbiter: cannot open kernel arbiter, no multi-card support

looks interesting but it even works with 2 cards in the first case, just not with the output I want.

Section "Device"
        Identifier "RX580"
        Driver "amdgpu"
        BusId "PCI:7:0:0"
EndSection
Section "Device"
        Identifier "HD4850"
        Driver "radeon"
        BusId "PCI:6:0:0"
EndSection
Section "Monitor"
   Identifier  "Acer"
EndSection
Section "Monitor"
   Identifier  "Medion"
EndSection
Section "Screen"
   Identifier  "Primary"
   Device      "RX580"
   Monitor     "Acer"
   SubSection "Display"
       Modes       "1920x1080"
   EndSubSection
EndSection
Section "Screen"
   Identifier  "Secondary"
   Device      "HD4850"
   Monitor     "Medion"
   SubSection "Display"
       Modes       "1280x1024"
   EndSubSection
EndSection
Section "ServerLayout"
    Identifier  "DefaultLayout"
    Screen  0   "Primary"
    Screen  1   "Secondary" RightOf "Primary"
EndSection

Does someone have an idea how to configure X to use both GPUs, one for each monitor?

Further information:
My system: CPU: Ryzen 1600 (no iGPU), Motherbord: ASUS Prime 350 Plus.
My system is up to date (pacman -Syu).
I also use the computer for VMs with PCI passthrough but that is disabled currently.

Edit:
Of course it was an HD4850, not an HD4770, I was stupid.
Also I thought the 2nd DVI Port was also from the 4850 but it was in fact on the RX 580.

Last edited by Rynak (2019-06-24 21:17:38)

Lone_Wolf · 2019-06-24 11:46:58

[    22.840] (II) AMDGPU(0): glamor X acceleration enabled on Radeon RX 580 Series (POLARIS10, DRM 3.30.0, 5.1.12-arch1-1-ARCH, LLVM 8.0.0)

[    22.842] (II) AMDGPU(0): Output DVI-D-1 disconnected

[    22.852] (II) RADEON(G1): glamor X acceleration enabled on AMD BARTS (DRM 2.50.0 / 5.1.12-arch1-1-ARCH, LLVM 8.0.0)

My RX 580 does have a DVI connector, is it not present on your card ?

Also it doesn't look like you have a HD 47770 but a later videocard in this system.

post lspci -knn please.

Rynak · 2019-06-24 21:25:26

Lone_Wolf wrote:

My RX 580 does have a DVI connector, is it not present on your card ?
Also it doesn't look like you have a HD 47770 but a later videocard in this system.

Ehm I am a bit stupid I guess. Yes, it has an DVI connector, I thought it was from the graphics card below. Also Yes, it was an HD 4850, not 4770. I confused them because I used a 4770 until recently.

Here is the lspci -knn.

Now that I noticed the RX580 has a DVI port I tried to use it. However, when I boot Linux (I removed the 2nd GPU for the test, also tried USB Arch ISO and Linux Mint ISO) the systemd messages appear on screen up to some point where everything turns black. I guess it is the points where the graphics drivers are loaded (kernel mode setting).
So the DVI port apparently does not work as soon as the drivers are loaded ...
I can plug in the DP cable to log in etc, but also xrandr shows me no connection on the DVI port.

But I guess this is a topic for another thread or maybe a different forum.

Last edited by Rynak (2019-06-24 21:26:35)

Lone_Wolf · 2019-06-27 12:07:47

up to some point where everything turns black. I guess it is the points where the graphics drivers are loaded (kernel mode setting).
So the DVI port apparently does not work as soon as the drivers are loaded ...

That suggests the problem is with your graphics environment.
Try booting with systemd.unit=multi-user.target as kernel parameter.
(That will take to you to a console login screen instead of graphical environment)

Last edited by Lone_Wolf (2019-06-27 12:08:05)

Arch Linux

#1 2019-06-21 18:54:05

Using 2 monitors with 2 discrete GPUs (Radeon RX 580 + HD 4850)

#2 2019-06-24 11:46:58

Re: Using 2 monitors with 2 discrete GPUs (Radeon RX 580 + HD 4850)

#3 2019-06-24 21:25:26

Re: Using 2 monitors with 2 discrete GPUs (Radeon RX 580 + HD 4850)

#4 2019-06-27 12:07:47

Re: Using 2 monitors with 2 discrete GPUs (Radeon RX 580 + HD 4850)

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