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O Ocalhoun avatar Ubuntu

Radeon 4550 video card not detecting second monitor

cn flag
O Ocalhoun

On Ubuntu 20.04 with KDE installed on top.

It's a bit of a complicated setup, so please bear with me.

Primary video card: Radeon 5450 --> 1 VGA monitor, 1 DVI monitor (both working perfectly)

Secondary video card: Radeon 4550 --> 2 VGA monitors (one works perfectly, the other problematic and not working)

Tertiary video card: Radeon 4550 --> 2 VGA monitors (one works perfectly, the other not detected at all)

I just upgraded to a new motherboard. Previously the 'primary' video card was onboard intel graphics, and the entire system worked perfectly under Kubuntu 20.04. Now that I've made this hardware change and reinstalled the OS, though, both of the Radeon 4550s are working perfeclty fine with the first monitor, but cannot properly detect or output to the second monitor on each card.

Also tried installing Kubuntu 20.04 (what I'd been running previously, successfully using all 6 monitors) and had exactly the same issue.

One of the 4550s just can't detect the second monitor at all. Everything on the software side tells me I have only 5 monitors connected instead of the 6 there should be. The other 4550 seems to know that there's a monitor connected, but only detects it as "DVI-2-2", with a max resolution of 1024x768. That monitor doesn't detect any signal from the video card and doesn't display anything.

Output of xrandr --listmonitors:

xrandr --listmonitors
Monitors: 5
 0: +*DVI-0 2560/597x1440/336+1080+1080  DVI-0
 1: +VGA-0 1920/480x1080/270+1080+0  VGA-0
 2: +DVI-2-2 1024/271x768/203+1080+1080  DVI-2-2
 3: +DVI-1-0 1920/510x1080/287+3640+1080  DVI-1-0
 4: +DVI-1-1 1080/480x1920/270+0+1080  DVI-1-1

Output of xrandr --listproviders:

xrandr --listproviders
Providers: number : 3
Provider 0: id: 0x56 cap: 0x9, Source Output, Sink Offload crtcs: 4 outputs: 3 associated providers: 2 name:ATI Radeon HD 5450 @ pci:0000:21:00.0
Provider 1: id: 0xba cap: 0x6, Sink Output, Source Offload crtcs: 2 outputs: 3 associated providers: 1 name:ATI Radeon HD 4550 @ pci:0000:4a:00.0
Provider 2: id: 0x95 cap: 0x6, Sink Output, Source Offload crtcs: 2 outputs: 3 associated providers: 1 name:ATI Radeon HD 4550 @ pci:0000:03:00.0

Maybe this is the kick in the pants I need to finally stop using such a crazy system (and probably move to supporting the extra monitors on USB-to-VGA adapters instead) ... but it would be really nice if I could find a software solution for this and not need to buy or install any extra hardware.

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guiverc avatar
cn flag
guiverc
You weren't specific as to kernel stack used for your install (Ubuntu LTS releases have two kernel stack choices; the default is set by the ISO used to install). Are you using a different kernel (& video) stack to your initial setup now? ie. maybe you were using the GA stack for your old install, but the re-install is on later media which defaulted to the newer HWE stack? If your new machine is using different GPUs (I wasn't sure, but you did mention intel for the older box), then maybe switching stacks may help. It's easy to test/install as you can have both installed & select at boot
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O Ocalhoun avatar
cn flag
O Ocalhoun
I'm using the 'generic' kernel, which is the same as what I was using on previous install.
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guiverc avatar
cn flag
guiverc
*generic* GA kernel? or *generic* HWE kernel? The G in GA refers to *general* and is a different thing to the type of kernel; eg. *generic* is the generic kernel, as distinct from say low-latency etc... which are options available to both GA or HWE kernel stacks.
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O Ocalhoun avatar
cn flag
O Ocalhoun
Oh ... then I'm really not sure how to check which version I'm on. And even less sure how to check what the previous system was.
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guiverc avatar
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guiverc
Ubuntu 20.04 LTS using the GA kernel stack is using the 5.4 *stable* kernel for the life of the product; where as Ubuntu 20.04 LTS using the HWE or *hardware enablement* kernel stack changes during the life of the product; 5.8 or the 20.10 kernel at 20.04,2, 5.11 or the 21.04 kernel at 20.04.3, 5.13 or th 21.10 kernel at 20.04.4 etc... `uname -r` is a quick way to tell what is running; but you can have both installed; you select which you use at boot with using `grub`
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O Ocalhoun avatar
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O Ocalhoun
Ah, finally found out I'm currently on HWE by running `dpkg --list | grep linux-image` and finding `linux-image-generic-hwe-20.04` in the results. Now I've got to look through the backup files and see if I can find a way to find out what that was running.
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