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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July 31st, 2008 at 12:18 am
Run a Google search on “purple pixels”…it may be a similar situation and you need to talk to Apple about it.
July 31st, 2008 at 6:42 am
Blame Greenpeace!
All the pressure on Apple to “go green” apparently is having unforseen consequences!
July 31st, 2008 at 8:37 am
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.
August 8th, 2008 at 8:09 am
@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!).
December 3rd, 2008 at 12:20 am
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
December 4th, 2008 at 10:40 am
@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.
December 4th, 2008 at 10:34 pm
Thanks. Looks like I’m off to my nearest Apple store this tomorrow.
December 27th, 2008 at 7:08 am
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…
December 29th, 2008 at 6:51 am
@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.
May 22nd, 2009 at 2:03 am
Here is a screen shot of what is I’m dealing with right now.
http://www.purei.com/mac_bugs/bug.jpg
July 31st, 2009 at 4:14 pm
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.