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Radeon VII cannot handle more than 2 displays (+ performance issues)

Question asked by baftac on Jun 29, 2019
Latest reply on Jun 30, 2019 by billy72
  • Issue Description: I actually have two/three issues which might be related, therefore I dont want to create two separate threads here.
    • First issue: It looks like my GPU cannot handle more than two monitors. (Possibly related issue: Radeon VII flickering and artifacts when attaching a second monitor.) I have a 3-monitor setup (had a GTX970 before) which could even be handled by my onboard intel gpu. For the following scenarios, consider the following key-maps:
      • Monitors are labelled AA, BB, and CC (see below for the respective models). All monitors work fine via DisplayPort and HDMI (verified when used with the old GTX970 and onboard graphics)
      • GPU Ports are labelled as follows:
        • DisplayPortDP_1 (farthest away from HDMI port), DP_2DP_3 (right next to HDMI)
        • HDMI: HDMI
    • First issue (scenarios): When collecting information on that issue, I started with the following working setting:
      • (works)
        BB DP_1
        CC HDMI
      • I then wanted to connect my third monitor:
      • (does not work)
        BB DP_1
        CC HDMI
        AA DP_2 --> Monitor is not being detected, Monitor itself thinks that it gets an input (auto turn on), after a few seconds it shows a "No signal" message and turns off again -> repeats endlessly
      • (does not work)
        BB DP_1
        CC HDMI
        AA DP_3 -> monitor is being detected but max. allowed resolution for it is 960xsomething (keep in mind, all monitors are 1920x1080)
      • Then, I tried the following combinations:
      • (works)
        BB DP_2
        CC HDMI
      • (does not work)
        BB DP_3 -> max resolution 720p
        CC HDMI
      • (works) - This is the setting which I'm currently using, the third monitor sits next to me (unused)
        AA DP_1
        BB DP_2
      • (does not work)
        AA DP_1 -> detected (with correct resolution) but monitor receives no signal
        BB DP_2
        CC HDMI
      • Yesterday, I also received my new Index VR headset and wanted to connect it. It didnt work. Only if I unplug one of the two monitors, I can connect my VR headset and get a picture on it.
      • What I gather from this:
        • The graphics card is unable to handle more than 2 monitors
        • The DisplayPort 3 (the one next to the HDMI port, I dont know its actual internal number) seems to be not working correctly at all.
      • When I bought this GPU, I hoped that I can connect two monitors via DP, one via HDMI, and the VR headset via the last DP port..
    • Second issue: Bad performance
      • In some games (e.g. ETS2) I get the same or less fps than with my old GTX970 (This was tested on both, Ubuntu 18.04 and Arch)
      • The unigine superposition benchmarks give me really low results (partly significantly) lower than other benchmarkers' results on their result lists, with the same graphics card.
    • Third issue: screen artifact on VR headset
      • When playing with the Index VR headset (connected to DP_1, whereas another monitor is connected to DP_2), I see a small rectangle on the right, which looks like a distorted monitor (purple-greenish garbage). It doesnt look like its an issue caused by the headset but I'm also not 100% if it is caused by my GPU (given the other problems I have, I really think it is though)
    • Info: I don't have a windows system at hands, so I cannot verify whether this might be a Linux-driver related problem or something related to my hardware. Any hints/tips on stuff that I can try is appreciated!
  • Hardware:
    • Graphics card: Sapphire Radeon VII
    • CPU: Intel i7-4790k
    • Motherboard: ASUS Z97-A
    • RAM: 32GB (4x8) DDR3
    • PSU: EVGA Supernova 750W G2
    • Monitor 1: (AA) AOC G2460P
    • Monitor 2 (BB): AOC G2460PF
    • Monitor 3: (CC) AOC G2460P
  • Software:
    • Arch Linux, kernel: 5.1.14.a-1-hardened (issues can be reproduced with normal linux kernel as well)
    • Latest graphics drivers from the Arch repos: 4.5 (Compatibility Profile) Mesa 19.1.0
    • KDE

 

THANKS FOR YOUR HELP!

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