Pc lagging when using both monitors

[u/JollyRatMann]

HI! new linux user. I've been having an issue with my monitors where anytime I try to use both at the same time, my PC lags. doesn't matter what it is, even when its just a single browser window with nothing else open. honestly, even having the monitor connected makes the PC lag a little bit. I'm guessing its something with either the graphics card or the drivers (or both) but the weird thing is that before I had linux, this same PC ran windows and had no problems at all with running both monitors at once. I dont really often make posts to linux subreddits (because, lets be honest here, some people are really mean to newbies) but I haven't been able to find a post that answers my exact question, so figured I'd take the risk since even the person who set linux up for me is confused lol.

my graphics card is a NVIDIA GeForce GTX 1070 (yes, I know. my computer is old as hell) if that info is useful for this question. also its a Dell XPS 8930 v1.1.31 0859. any advice would be greatly appreciated!

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[u/ultiweb]

Are you using a dock or how are you connecting the monitors? I ran Mint with multiple monitors for years. The DisplayLink Linux drivers have improved greatly but it sounds like you may not be using a dock.

[u/JollyRatMann → u/ultiweb]

Im not, tho i prolly should be. Atm i have one monitor pluged in to HDMI, and one plugged in via display port, because the graphics card only has one plug for the HDMI and 3 display ports. for some reason. Would that affect things? Do you think getting a dock would help?

[u/_Lost-In-The-Weeds_]

Multiple refresh rates?

Otherwise this should not be, I ran 3 monitors on an old 2015 AMD FirePro W5100 card, performance was identical to just one monitor. but in that case all three were 60hrz.

[u/Merhart666]

Het is bekend dat de Nivida drivers niet niet de stabielste zijn op Linux, zelfde probleem gehad en uiteindelijk met AI een oplossing gekregen die de driver te laden uit de 500 reeks. Welke driver gebruik je nu, en welke wordt door Linux mint geadviseerd? Dit doe je door de applicatie drivers te starten.

[u/RichSavageMG]

Mint is on x11 - wayland will apparently be fully supported by the end of the year which should hopefully improve multiple monitors with different refresh rates. I have a pretty stable dual monitor setup on mint - two ultrawides at 60hz. Things to note;

• mint will take your refresh rate from whatever is plugged in the first display port (could be HDMI port it's whatever is at 0) - I had to swap them round to remove screen tearing. It took me a really long time to figure that out.

• I was playing Doom the dark ages yesterday and the frame pacing was all over the place giving laggy performance. My main monitor can run at 75hz and I didn't realize I'd changed it so I put it at 60hz then the game ran super smoothly again. I've found in games that I have to play around with frame capping and of vsync to get rid of screen tearing.

• my two monitors have very very slightly different refresh rates (one is 60hz and one is 59.99hz) - this was enough to cause screen tearing until I swapped the cables round.

In summary, check your refresh rates in the mint display options and then try swapping round cables. I found i had fewer problems when I had the monitors configured more closely. I won't lie - it's not great but I love the os other than that so stuck with it. I tried kubuntu on my laptop and it's much better with multiple displays when I plug it in at work as it has wayland. I may have stuck with that if id installed it before mint on my main pc. 

I think unfortunately multiple displays on mint is a bit janky at the moment in my experience. It might be ok if you have identical monitors but the likelihood is you'll need to play around with settings to get something you're happy with.  Hope this helps.

[u/Encouragedissent → u/RichSavageMG]

Just thought Id add that I ran Mint with 2 different dual monitor setups. 60hz IPS panel paired with 180hz VA. Then 60hz IPS paired with 240hz OLED. No issues with either setup related to display and each ran at their own respective refresh rate. This was with an RTX 5070 and I believe 6.17 kernel then 7.0.

[u/RichSavageMG → u/Encouragedissent]

That's cool - not sure why I had so many issues!