Random green pixels on my Mac display

This is most strange. In recent weeks I’ve started seeing individual green pixels randomly appear on my iMac screen:

My first thought was that I had some stuck pixels on my display. But now I don’t think so.

For one thing, if there was a physical problem with the display, I wouldn’t be able to screen-grab the green pixels (as shown above). Also, they appear fairly randomly on the screen; they’re not in the same position each time (though they seem to cluster around the upper portion of the screen).

The pixels only appear when the content “underneath” them is stationary. For example, if I drag an image window around in Photoshop then there are no green pixels, but when I stop dragging then one or two green pixels appear in the image window after around half a second.

It seems to only happen when the content on the screen is dark-ish – for example, they’re very noticeable when opening Front Row – but that might just be because they’re light green.

Also I’ve just done some testing, and the pixels only appear when the display is in “Millions” colour mode. When I switch to “Thousands” colour mode the pixels don’t appear.

Frankly, I’m stumped. If it’s not a display issue, is it a problem with the graphics chip? But then again, I only noticed the problem since upgrading to Leopard a few months ago. Graphics driver problem? Some sort of issue within Leopard? It sounds vaguely similar to the problem in this Apple discussion thread – which would indicate dodgy VRAM – but unfortunately there’s no example screenshot to compare with.

What’s more, the problem seems to be getting worse by the week, with more and more pixels appearing, and – ooh – I’ve just noticed my first ever blue pixel.

Anyone ever seen anything like this? My graphics card is an ATI Radeon X1600. Is my Mac slowly dying? Heeeeelp! :(

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15 Responses to “Random green pixels on my Mac display”

  1. Joe Says:

    Run a Google search on “purple pixels”…it may be a similar situation and you need to talk to Apple about it.

  2. Steve P Says:

    Blame Greenpeace!

    All the pressure on Apple to “go green” apparently is having unforseen consequences!

  3. DWalla Says:

    My bet would be the VRAM. Symptoms are very consistent with a failing video card. I’ve seen a lot of video cards fail over the years and yours sounds like it’s on the brink.

  4. Matt Says:

    @Steve P: Very good :)

    @DWalla: I think it probably was related to the video hardware. I’ve now had the logic board replaced and the green pixels have gone – and what’s more, the GPU is now running a lot cooler (around 55 degrees C instead of 70 degrees C!).

  5. Dave H Says:

    I think I have an extreme version of the same thing on my 4 year old Powerbook. I seems to be worse when it hasn’t been used for a while. These green pixels often appear first in the folder thumbnails and then progress to framing the finder window. Finally the screen has loads of lines across it and jumps like a TV going out of tune. It seems to sort itself out after around 10 minutes but it still doesn’t look perfect.

    It seems that I need a new video then. Should this fix it? Any thoughts gratefully recieved

  6. Matt Says:

    @Dave H: I’m no expert, but yes it sounds like your video card is on the way out (possibly its RAM). Though you could try running the hardware test and/or reinstalling Mac OS to confirm.

  7. Dave H Says:

    Thanks. Looks like I’m off to my nearest Apple store this tomorrow.

  8. Aaron S Says:

    I actually just bought a brand new 8-core Mac Pro in August 08, upgraded to 4 gigs of RAM, and I’m having this exact problem with green and purple pixels…

  9. Matt Says:

    @Aaron S: Sounds like you might want to get it fixed under warranty in that case! Do Mac Pros have separate video cards? If so then you might only need the card swapped out.

  10. Pat Reilly Says:

    Here is a screen shot of what is I’m dealing with right now.

    http://www.purei.com/mac_bugs/bug.jpg

  11. Shi Says:

    Have a mack pro quad 2.66 and mine seems to have started after updating to leopard. I’m thinking about going back to 10.4. My gut tells me it’s an operating system or quicktime ting. final cut has been doing some dodgy display things as well. I guess it could be the v card but allot of people with different hardware are having similar problems.

  12. Rotten Apples Says:

    3 weeks ago I bought a new quad-core iMac (i7). The first machine had a burnt out pixel on the display, so two weeks later I exchanged it for a new machine (same make and model), which is the one I am using now. I am running into this green pixel issue too, but it’s not just one or two pixels, it’s entire regions in images where the colors are darker. I’m super annoyed with this… especially with this being the 2nd machine that I’ve swapped out with Apple.

    It happens when the machine awakes from a semi-long sleep, and the problem persists for about 4 or so minutes, and then it magically stops. WTF Apple? I can’t be totally bitter because it’s under warranty and I also have applecare for it, but this is just lame. Once again, undoubtedly, I am sure I am going to have to make an appointment with a “genius”, haul my ass and the machine to the mall, prove my case, deal with lame Apple staff, swap it out and reinstall all my software for a THIRD time. Apple should be paying me for as much downtime as I’ve already had dealing with their faulty and defective hardware (and also what is becoming their lame staff). This blows.

  13. boescha Says:

    Hi all,

    i have the exact same problems with the green dots. But they don’t appear when i boot up windows using bootcamp. I don’t really get it. My dots also disappear, when i use only 32000 colors…

    weird.

  14. Matt Says:

    @Rotten Apples: Sounds like you’ve had an unlucky streak with your iMac – I hope you have a working one now…

    @boescha: In case you missed the update to this story, it turned out to be the GPU, and I had to get my logic board replaced. Works like a charm now.

  15. Genus Says:

    @Rotten Apples
    I just gotten my iMac (core i7). on the first boot i had a lot of these green dots on the great screen. then the system rebooted and all was fine… for about 4 days then i noticed them re-appearing after long sleep. That really is disappointing, especially having paid over $2,000, quite a price for a lemon.

    now I’m gonna to get it resolved with apple.