[SOLVED: GPU upgrade] Stopping lag when using multi monitor with 1x4k on Linux

Hey guys!

So I just got a 4K (AOC U2868PQU) screen at work (I'm a software developer), and I've been trying to get it setup on my PC. Running Linux Mint 17 with the 3.13.0-24-generic kernel.

Currently I'm running 2x AMD HD5570's and was running 4 screens, 3 off one and 1 off the other in this configuration:

$ lspci | grep VGA
02:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Redwood PRO [Radeon HD 5550/5570/5630/6510/6610/7570]
03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Redwood PRO [Radeon HD 5550/5570/5630/6510/6610/7570]

First card:

  • DVI 1920x1080
  • HDMI 1600x1200
  • DP 1920x1080

Second card:

  • DVI 1920x1080

So that worked sweet using the open source drivers. So I get this 4K screen and set it up like so:

First card:

  • DVI 1920x1080
  • DP 3840x2160

Second card:

  • DVI 1920x1080
  • DP (->DVI) 1920x1080

But the open sources drivers don't support 4K, so the 4K screen was stuck at 1080i. So I installed the fglrx drivers and now I get 4K, but only two screens can be enabled (in arandr). I made the mistake of not installing the CCC however.

But it is SOOO LAGGY, on both the screens now. Is this a driver issue? Or a GPU issue? My boss said I can upgrade the video card (I'll prob stick with just 3 screens this time on a single card).

So if this is just a case of the 4K screen being too heavy for the little old 5570's, what graphics card should I get? I don't mind nVidia or AMD, just as long as I can drive 3 screens without having to wait for the mouse to come along.

Thanks for your help!

I'm going to go install the latest kernel, and re-install with CCC to see if I can get better performance (but I'm not hopeful).

UPDATE: OK installing 3.19.4 kernel, with the open source drivers got me 3 screens, but it's still laggy :(

UPDATE: Tried to re-install the fglrx driver but it won't compile against 3.19.4 :(

UPDATE: moved to Linux category as probably more suited here

I wonder if a 3.19-* kernel and flgrx would fix your issue... maybe try installing ubuntu gnome 15.04 nightly (which is surprisingly stable for me) on a small separate partition to test, because it packages flgrx that will compile against 3.19-* kernels.

Also, I've experienced the supreme lag of the cinnamon gods before too. Not sure what causes it, but it only occurs for me post screenlock, and I fix it by restarting cinnamon.

For the binary drivers on 3.19 or higher (worth noting Linux 4.0 is available) use the fglrx 15.* drivers.

Also mesa is very important on the graphics stack, having the latest mesa and drivers will help. Current mesa is 10.5.3.

Arch and gentoo have some good tips on radeon drivers https://wiki.archlinux.org/index.php/ATI
https://wiki.gentoo.org/wiki/Radeon

Ah OK, I am using Cinnamon so maybe that is the issue. I'm not too partial to it, so might be time to try something else. I would be keen to go to Ubuntu because I've had mega issues getting Gnome3 to work on Mint, which sucks because mint is so polished.

I didn't know there were 15.* fglrx drivers out (are they beta?), I should've mentioned I was using 14.20 which I thought was the latest.

I kinda bricked my machine now, I force uninstalled the fglrx drivers and now X won't start. I can still use the VTY's but it's not so useful for webdev. Tried running dpkg-reconfigure -a --force but that didn't fix it.

So if I can't get the 15.* drivers going, looks like I'll be hitting up Ubuntu.

Cheers for that Archwiki link, I'll check that out.

Well I ditched Mint in favour of Ubuntu 15.04. Running the 3.19.0-15 kernel and fglrx.

Unfortunately, my dual 5570's still wouldn't all of the screens. But the boss bought me an ASUS R9 270 2GB and now it does all of them sweet as, no lag.

Now there are just a few little niggles, I need to find out how to do some per screen X settings...

  • The mouse seems very slow on the 4K screen, but fast on the 1080p screens - of course due to the higher res. So I'm trying to find a way to increase it on one and not the other.
  • The 4K screen has so much real estate it's hard to read some stuff... looking for a way to adjust the scale on just that screen

Apart from that it is great! Will see if I can run a 4th screen after I get some work done, although I heard the HDMI is mirrored off one of the DVI ports.