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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Notebooks > Green pixel waves on external display.

Green pixel waves on external display.
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Trygve
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Feb 27, 2009, 08:31 AM
 
I have a Late 2008 MacBook Pro 17 (the last to be DVI-based). 2.66GHz, 4GB, 320HD, HiRes Matte Display. I have it hooked to a 30" Apple Cinema Display.

The effect I am seeing has happened 3 times. 1) The first time I started it after removing it from the box and restarted after updating the OS via System Update. It did it again a few minutes later after installing a second System Update. Both times it was during the weird "fast reset" that happens after updating the OS. Then all was fine for 36 hours or so and it did it out of the blue.

What I get is a series of wavy lines that are not really lines at all - more like "connect the dots" with hundreds, perhaps thousands of green and blue pixels that follow the contours of whatever image is on the screen.

http://www.xericdesign.com/blogpics/greenblue.jpg

The grayish moire pattern is a result of the camera and is not on the real monitor. Only the green and blue pixels are the issue. They change shape depending on what is on the screen, and only affect the external display.

The only way to fix is a full restart, shutdown, or unplug and replug the DVI connector.

Is this a bad NVIDIA board? I purchased this Jan 3, 2009 or so but then had to leave the country till yesterday so it only got unboxed yesterday.

MacBookPro 17 Mac OS X (10.5.6)
     
Trygve  (op)
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Mar 2, 2009, 08:17 PM
 
It happened again just now. Turning on mirroring or changing the resolution do nothing. Restarting does cure it. In Console, I see:

3/3/09 12:08:19 AM [0x0-0x1f01f].com.apple.systempreferences[177] objc[177]: Class O3Panel is implemented in both /System/Library/MonitorPanels/AppleDisplay.monitorPanels/Contents/Resources/Contrast.monitorPanel/Contents/MacOS/Contrast and /System/Library/MonitorPanels/AppleDisplay.monitorPanels/Contents/Resources/Geometry.monitorPanel/Contents/MacOS/Geometry. Using implementation from /System/Library/MonitorPanels/AppleDisplay.monitorPanels/Contents/Resources/Geometry.monitorPanel/Contents/MacOS/Geometry.

Thoughts?
     
ibook_steve
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Mar 2, 2009, 08:40 PM
 
Bad or dying GPU, unfortunately. What resolution is this at? Have you tried it at lower resolutions? Do you have the same problem at lower resolutions?

Steve
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Trygve  (op)
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Mar 3, 2009, 12:09 AM
 
This happens only on the external display, which is a 30" cinema display. Normally it is 2560x1600, but changing the resolution does not change the shape of the green pixel stuff - it just scales the same as the rest of the screen. I also get a light green line on the left side of widows about 1cm outside the window frame. These move with the window. There are a few green pixels that appear along the dock as well.

Since restarting cures it, I am wondering if it is software or hardware. I can't repeat it, but it seems to happen every couple/few days. The machine is just a week or so old and has run for perhaps 100 hours.
     
ibook_steve
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Mar 3, 2009, 12:43 PM
 
Unfortunately, probably hardware. It's happening because the GPU is warming up over time, and the heat is causing the VRAM to get corrupted, causing random pixel errors. You should be able to simply get a warranty repair since the machine is new.

If it's currently not showing up on the internal display, it probably will eventually.

Steve
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Trygve  (op)
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Mar 3, 2009, 07:24 PM
 
Why would a restart fix it then? When it happens, a restart cures it for days. The machine is never turned off.
     
ibook_steve
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Mar 3, 2009, 08:01 PM
 
VRAM is reset and initially loaded with correct screen display data. It's only after the machine has run a while that the corruption is appearing in the VRAM.

This is pretty much textbook corrupted video RAM.

Steve
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Trygve  (op)
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Mar 12, 2009, 01:04 PM
 
So it has been doing this every few days. It just did it again, and I ran TechTools on it and the RAM and VRAM passed. When TechTools filled the screen, there was no green or blue pixel weirdness, but now thT I am back in Finder etc, it is there - along the edges of windows and in small waves all over the place.

Could it be software? Would it be worth reinstalling everything?

Sleep/Restart fixes it too.
     
ibook_steve
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Mar 12, 2009, 06:26 PM
 
As I've already said, this is not software. This is graphic corruption by the GPU, specifically the VRAM. Trust me. I worked at Apple on the 12" Powebook internal and external video interface. I know what GPU video corruption artifacts look like. Just because the chip passes a simple diagnostic test does not mean that this is software.

Steve
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polendo
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Mar 12, 2009, 08:27 PM
 
I would have to agree with Steve. But.. just in case.. change the cable of the display. I have seen similar problems because of the cable.
     
Trygve  (op)
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Mar 21, 2009, 02:34 PM
 
Change the 30" Cinema Cable? It doesn't seem like a cable since sleep fixes it and flexing the cable does nothing.
     
Cold Warrior
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Mar 21, 2009, 02:50 PM
 
Steve provided the answer three weeks ago. The obvious solution is to now get Apple to repair it.
     
   
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