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  1. #1


    Member Since
    Dec 18, 2010
    Posts
    2
    Unhappy iMac graphics issues, I'm lost
    Hello everyone!

    I've been having this problem for a while now and haven't found a solution. At this point, it's either something terribly complicated or something so simple I need to be laughed at for hours on end. Either way is fine, as long as I have an answer.

    Bear with me, yes? The more information the better.

    Ever since I had my graphics card replaced the computer is glitching. Odd lines appearing, windows smearing when I move them and so forth, sometimes worse. These don't happen very often, but something is clearly amiss.

    What's worse, on the grey startup screen I get bright pink and yellow pixel blocks on top of the screen. They are also visible when I start from DVD. So far, they are no visible in Finder. When I boot Windows (XP professional, if that's important), I get the same blocks of pixel on top of the screen, only bright blue and green and significantly more of them. These have gotten brighter as time went by.

    What I've tried so far:
    - system updates (I do them regularly)
    - repaired permissions
    - run apple hardware test (came out clean in several attempts)
    - reset VPRAM
    - run TechTool Pro test (came out clean again)
    - I completely deleted and reinstalled my system and installed no new programmes for a while to see if there was a software conflict somewhere (this made no difference either, and the glitches were visible during installation)
    - completely reinstalled Windows, it's glitching even in the installation screen
    - updated drivers in Windows manually (glitch remained entirely unimpressed)

    Now, like I've said, this might be something really really simple and I'll never live it down, but I'm really at a loss. I don't know what to try, really. It might be a software issue, but since its so persistently cross-platform and independent of what software is running, I doubt it. I just don't get why all the diagnostics programmes don't find anything.

    I'm attaching screenshots of the two most common problems.

    I'm running a iMac Inter Core 2 Duo/3.06 GHz with 2GB RAM under Snow Leopard 10.6.5. The card in question is a NVIDIA GeForce 8800 GS using the latest Forceware driver (not sure about the version, but every version I tried looked exactly the same). If you need additional info, let me know.

    I'm guessing the card is fried, despite what everyone tells me. Money is a bit thin currently, so I'd very much prefer if it wasn't.

    So, what do you say?
    Attached Images Attached Images

  2. #2

    bobtomay's Avatar
    Member Since
    Dec 22, 2006
    Location
    Texas, where else?
    Posts
    26,465
    Specs:
    15" MBP '06 2.33 C2D 4GB 10.7; 13" MBA '14 1.8 i7 8GB 10.11; 21" iMac '13 2.9 i5 8GB 10.11; 6S
    Not really any doubt in my mind, that is a bad video card.
    I cannot be held responsible for the things that come out of my mouth.
    In the Windows world, most everything folks don't understand is called a virus.

  3. #3


    Member Since
    Dec 18, 2010
    Posts
    2
    Quote Originally Posted by bobtomay View Post
    Not really any doubt in my mind, that is a bad video card.
    Yes, I was afraid this would be the outcome. Thank you for the quick reply!

  4. #4

    hugtheslug's Avatar
    Member Since
    Feb 19, 2008
    Location
    Kent, UK
    Posts
    528
    Specs:
    2008 Unibody MacBook / 2009 White MacBook / iMac C2D 2.16 GHz 20" / iMac G5 1.6 GHz 17"
    Whoever installed the graphics card may have not seated it properly, and also the work should be guaranteed in some way.
    I would take the iMac back to them.

    Cheers

    Hugh
    A little knowledge is a dangerous thing.
    Warning - this user has only a little knowledge

  5. #5

    chscag's Avatar
    Member Since
    Jan 23, 2008
    Location
    Fort Worth, Texas
    Posts
    48,030
    Specs:
    Late 2013 27" iMac, iPad 3, iPhone 6s+, iPhone 6+, 3 iPods, El Capitan
    @hugtheslug

    The graphics card in an iMac (with the exception of the 27" model) is soldered onto the logic board. He has an older model, so his GPU is non-removable. The entire logic board has to be swapped out.

  6. #6

    hugtheslug's Avatar
    Member Since
    Feb 19, 2008
    Location
    Kent, UK
    Posts
    528
    Specs:
    2008 Unibody MacBook / 2009 White MacBook / iMac C2D 2.16 GHz 20" / iMac G5 1.6 GHz 17"
    Ah, sorry, forgot that.
    All the same, there should be some comeback on the logic board.

    Cheers

    Hugh
    A little knowledge is a dangerous thing.
    Warning - this user has only a little knowledge

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