Three Monitors Issues

Help Desk
1

I’m currently running Kubuntu 19.10 with kernel 5.3.0-42-generic and a ROG Stirx RX 570 graphics card. The card has 4 video out ports; 2 dvi, 1 hdmi, and 1 display port. I’m currently running two monitors. One is through the hdmi and the other is through dvi using a dvi to hdmi cable.

I recently moved and to save space connected a Mac Mini to the large screen 4k tv. That gives me an additional 27 inch monitor. The extra monitor had dvi and hdmi ports. Yesterday I connected the third monitor to the dvi ports on the graphics card and the monitor but the monitor wasn’t receiving a signal.

Is there an issue using both dvi ports from the gpu in linux or are three monitors generally a problem in linux? I’d like to find out before ordering a display port to hdmi cable. No reason to order it if it probably won’t work. Thanks

2

So, to be clear, you have the following connections:

  1. HDMI out to HDMI in.
  2. DVI out to HDMI in.
  3. DVI out to DVI in.

?

Edit: The reason I’m clarifying is because even though going from HDMI to DVI is a passive adapter piece of cake, going from DVI to HDMI is not always easy. Some DVI is dual-link, which basically means that there are two signals going through at the same time. HDMI however is single link and can’t receive the dual-link signals correctly. You can buy active converters that can attempt to mitigate this, some use a usb connection to help facilitate, but sometimes the monitors just won’t work with this setup.

Edit 2 Electric Boogaloo: Just in case I don’t get back to the forum tonight, Know if you’re using like a weird AMD Eyefinity, or if your monitors are different models, AMD card won’t necessarily function with more than two passive connected displays.

3

Thanks for responding I have to monitors connected. One going from hdmi to hdmi and another going from dvi to hdmi. When I connected another monitor using dvi to dvi it wouldn’t pick up a signal.

The working monitors are Acer and are the same model. The third monitor is an Asus.

4

I’m running Manjaro KDE on a spare SSD and the three monitors are running fine once I got the settings figured out in display settings. Maybe it’s a Kubuntu thing or the newer kernel fixed it.

5

I dont know what the issue was with your Kubuntu setup because I have been using 3 Monitors with Kubuntu 18.04 for years now and I dont have any problem with it. I also switched to Manjaro KDE recently for an evaluation period and there doesnt seem to be an issue there either.

However, it could totally be the connector with your monitor and how well it works with various ports. For example, the reason I think my 3 monitors have no issue at all is because I use HDMI ports from the monitors always.

I have 2 HDMI and 1 DVI so I bought an HDMI to DVI adapter for my GPU. This way allows me to always use HDMI cables to connect the monitors to the computers and for the DVI port the adapter makes it compatible with HDMI cable.

This might be a reason for your issue, maybe your monitors don’t support some ports as well as others. For example, I have one monitor that works like crap on Displayport but works wonderful over HDMI so I always use HDMI with it.

6

Thanks Michael, I’ll look into getting another dvi to hdmi cable for future use.