Display issue (pixel rendering) when discrete GPU is on

Discussion in 'MacBook Pro' started by Hippocrates, Jul 30, 2012.

  1. Hippocrates, Jul 30, 2012
    Last edited: Aug 1, 2012

    Hippocrates macrumors member

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    Jun 12, 2012
    #1
    *****latest update: problem solved by reinstalling mountain lion. Moderator, please help delete this thread, thanks :)



    I'm running ML on a rMBP. I noticed that whenever my VLC is opened (regardless of whether a movie is running, VLC is active or just in the background), opening the launchpad will lead to pixel rendering problem where there are tiny red flickering pixelated squares on the screen which disappear soon after emerging. Sometimes they will stay on though (shown in the image).

    [​IMG]

    Anyone has an idea of what's going on? I hope it's not a hardware problem as I'm nearing the 14th day of return period.
     
  2. Queen6 macrumors 603

    Queen6

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    #2
    I have not observed anything like this on my Retina, however it`s not with me now to confirm. VLC calls for the Discrete GPU, are you using gfxCardStatus to hold the system on the integrated GPU?

    I use VLC and there has just been a very recent upgrade to bring it in line with the Retina Mac`s. In general i tend use the app then close it, which would explain why i haven't seen any graphical anomaly as yet. i will try and reproduce later this evening.
     
  3. Hippocrates thread starter macrumors member

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    Jun 12, 2012
    #3
    Thanks. I'm using the latest version of VLC which I just downloaded a day ago. I do not have gfxCardStatus installed either. Automatic graphics switching is turned on for me.

    Just another observation, the flickering is more likely to occur after opening a movie in VLC, and such abnormal behaviour persist even after the movie is closed. I also noted that it occurs more often when the 'Other' folder in the launchpad is clicked into (as you can see in the image and the red pixels are mainly in the black area).

    I believe it has something to do with the discrete graphics card because having Photoshop in the background can also trigger this.
     
  4. Queen6 macrumors 603

    Queen6

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    #4
    I tried to reproduce the issue and so far nothing switching directly from playback to Launchpad and with VLC idle in the background did not reproduce any graphical anomaly this was done battery with the Nvidia GPU. I am running gfxCardStatus, however it is set to "Dynamic" so effectively the app`s are making the call on GPU`s as per Apple.

    I cleaned up my Launchpad and deleted the "Others" folder, moving the icons to "Utilities" and the primary space, although I doubt this makes any difference.
     
  5. Hippocrates thread starter macrumors member

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    #5
    Thanks for testing it out :) I realise that this issue is more complicated than it seems. It didn't always happen with VLC though I would say that VLC increased the frequency of abnormality. Moreover, it only happened on "Others" folder (the portion where the background is dark grey). Switching the launchpad on and off rapidly made it more susceptible too. I wonder if this phenomenon is caused by the transition between integrated and discrete GPUs.
     
  6. Queen6, Aug 1, 2012
    Last edited: Aug 1, 2012

    Queen6 macrumors 603

    Queen6

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    #6
    So far I have not seen the same graphical anomalies on my 2.3 Base Retina, I also considered if it was due to the GPU`s switching, however even when forcing the GPU to switch I still observed no error. As every machine has a differing software load it`s difficult to replicate the condition 100% it may be due to an app in the background not compatible with the Retina, only additional background tasks I have running are gfxCardStatus (set to Dynamic) and ClamXav at present
     
  7. Hippocrates thread starter macrumors member

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    #7
    It's strange indeed. I've installed gfxCardStatus and can now confirm that the anomalies do not happen the integrated GPU is on. Strangely, if I forced discrete GPU on, there was just fast flickering of the red pixels which disappeared almost immediately and gave a normal look with "Others" folder. The red pixelated squares only came about when I left the setting at dynamic switching (in addition to programs like VLC or Photoshop which utilises dGPU being executed at that moment).

    I've no other program running at the background and I seriously hope that it's not a problem with my dGPU. Well, it doesn't affect my work at all, but I wouldn't want to have a defective machine. I didn't see such anomalies with Lion though, should I reinstall Mountain Lion?
     
  8. Hippocrates thread starter macrumors member

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    Jun 12, 2012
    #8
    Just a little bit more update.

    I can reproduce the display artifacts reliably.

    1) Discrete GPU must be on
    2) Display setting must be set at "Best for Retina" or higher. The two lower resolutions below it has no problem at all.
    3) The artefacts only manifest itself when switching fast between normal working screen and launchpad screen (exclusively when "Others" folder is opened, see image on first post).

    Based on experience, does anyone think this issue is software-based or hardware defect? Does it worth the effort if I try to wipe the disk clean and reinstall Mountain Lion?
     
  9. Queen6 macrumors 603

    Queen6

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    #9
    What does spring to mind is move your icons out of the "Others" folder, it will then be deleted and then recreate it and see what the result is. You could reinstall the OS, although I would try to exhaust other possibilities first.
     
  10. terraphantm macrumors 68040

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    #10
    External or internal display? I've gotten similar artifacts on an external display when the DVI cable was loose.
     

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