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Old 05-03-10, 04:25 AM   #1
luke bewsell
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Default Green / Pink Flashing Pixels 195.36.15

I'm reporting similar issues to what was stated in thread http://www.nvnews.net/vbulletin/showthread.php?t=131226 . The issue is that on some certain colours the screen will display bright flashing green pixels on the screen for that colour.

I've managed to isolate the colour causing the issue and made a background of it.



Stopping the framebuffer doesn't help.
Attached Thumbnails
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Name:	display.jpg
Views:	1773
Size:	89.2 KB
ID:	40158  
Attached Files
File Type: gz nvidia-bug-report.log.gz (42.8 KB, 113 views)

Last edited by luke bewsell; 05-03-10 at 04:26 AM. Reason: removed link
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Old 05-10-10, 08:07 PM   #2
luke bewsell
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Default Re: Green / Pink Flashing Pixels 195.36.15

anyone?
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Old 05-11-10, 10:41 AM   #3
danix
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Default Re: Green / Pink Flashing Pixels 195.36.15

Hi Luke,

I suspect this might be temporal dithering. Displays are not capable of displaying all of the colors in the 24-bit color space, so we use temporal dithering to help fill in the gaps. The effect is usually subtle, but I suppose there could be cases where a color falls into a wide gap in the range of colors the display can handle, and results in a harsher dithering effect.

You can disable temporal dithering by setting
Code:
Option "RegistryDwords" "DitherAlgo8=3; DitherAlgo6=3"
in xorg.conf's "Device" section. Does that make the issue go away?

Even if the issue does go away when dithering is disabled, it would help for us to see this first hand to make sure that dithering is working as intended. Can you attach an image file containing the actual color? Thanks.
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Old 05-11-10, 10:09 PM   #4
luke bewsell
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Default Re: Green / Pink Flashing Pixels 195.36.15

I've attached three files for you;
annoying_desktop.png (913 Bytes) - this is the file that cause the display issue in the original post
annoying_desktop_2.png (523 Bytes) - this is a new file that I've created with similar issues, just not as extreme as the first case.
monitor_annoying_desktop_2.jpg (59.1 KB) - picture of the annoying_desktop_2.png from the user

I've also tried the xorg.conf change and it hasn't done anything.
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Name:	annoying_desktop_2.png
Views:	191
Size:	523 Bytes
ID:	40218  Click image for larger version

Name:	annoying_desktop.png
Views:	181
Size:	913 Bytes
ID:	40219  Click image for larger version

Name:	monitor_annoying_desktop_2.jpg
Views:	226
Size:	59.1 KB
ID:	40220  
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Old 05-17-10, 05:06 PM   #5
danix
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Default Re: Green / Pink Flashing Pixels 195.36.15

Thanks for the samples, Luke.

Unfortunately I have not been able to observe the flashing myself. I tried matching your configuration as closely as I could, using the same GPU (Quadro FX 4800) and display (HP LP2475w). I tried connecting the display over single-link DVI, dual-link DVI, and single-link DVI via a DP-DVI dongle.

You appear to have two of these displays connected; one on dual-link DVI and the other over a DP-DVI dongle. Do both of these exhibit the flashing behavior? If only one, which one?
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Old 05-20-10, 07:48 PM   #6
luke bewsell
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Default Re: Green / Pink Flashing Pixels 195.36.15

Quote:
Originally Posted by danix View Post
You appear to have two of these displays connected; one on dual-link DVI and the other over a DP-DVI dongle. Do both of these exhibit the flashing behavior? If only one, which one?
Hi Danix;

The majority of cases we get generally occurs from running over the DP-DVI dongle. But I've also seen cases(notably my computer) where the DVI->DVI port also displays the same issues.

I've reseeded the graphics card, ram, etc find it clears up some of the issues. Sometimes restarting X or the computer may cause the problem to go away. After the initial first few dots appear on the screen this will progressively get worse over time. On a few computers running KVM with windows, you are able to switch back into windows and have no display issues at all.

Unfortunately I am unable to fail a working computer into this state.

I've also attached my latest gz.gif nvidia-bug-report.log.gz (34.3 KB) , which is running 190.42 . I've seen this occur on 195.36.15
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File Type: gz nvidia-bug-report.log.gz (34.3 KB, 112 views)
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Old 05-21-10, 03:49 PM   #7
danix
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Default Re: Green / Pink Flashing Pixels 195.36.15

Are you saying that it doesn't happen all the time on the affected machines?

Have you noticed any factors that seem to make it more likely to happen? Is it more or less guaranteed to happen if a display is left up for long enough?
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Old 05-23-10, 11:30 PM   #8
luke bewsell
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Default Re: Green / Pink Flashing Pixels 195.36.15

Quote:
Originally Posted by danix View Post
Are you saying that it doesn't happen all the time on the affected machines?
When the issue occurs it will generally never go away until one of the things happen:
- restart x a couple of times(reboot, ctrl alt backspace)
- reseeding of video card, ram, second cpu. can stop this or lessen the issue.
- Swapping out a monitor. i.e. I swapped out my monitor today with a samsung syncmaster 2443 to the display port. The secondary(DVI -> DVI) monitor is a HP LP2464, which has the pink/green pixels is now completely gone.


Quote:
Originally Posted by danix View Post
Have you noticed any factors that seem to make it more likely to happen? Is it more or less guaranteed to happen if a display is left up for long enough?
No, we do not have any conclusive evidence to what actually causes it to happen. I speculate something in the monitor may not be communicating with the graphics card.

I mention earlier of some of the computers running a kvm with windows, when swapped back into windows both monitors display properly. Then in linux you see the graphics pink/green pixels.
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Old 06-06-10, 09:47 PM   #9
luke bewsell
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Default Re: Green / Pink Flashing Pixels 195.36.15

Danix; Can I get an update?
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Old 06-07-10, 08:58 PM   #10
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Default Re: Green / Pink Flashing Pixels 195.36.15

Sorry, Luke, I was never able to get this to happen on the setup that I configured which was similar to yours. I've kept the annoying.png image as the desktop background on a couple of my main test machines, which have had a wide variety of GPUs and displays plugged into them over the past couple of weeks, and never saw any flashing pixels.

I've since had to return the monitor to the group I borrowed it from, but that was a while ago and it might be available again. I'll try to take another look soon.

Do you know if this happens if you have just one of these monitors hooked up, or only if you have two of them? I don't know if I'll be able to get two monitors, but if it seems like two are needed to observe this issue, then I'll try to get my hands on two. Could you give me a sense of how long the system might need to be up before this starts to happen? What firmware revision do you have on the monitors?
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Old 06-09-10, 12:26 AM   #11
luke bewsell
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Default Re: Green / Pink Flashing Pixels 195.36.15

Generally after a few weeks(2weeks>2months) of constant mon-fri 9-5 use. After the first initial spot it will get worse within the next 2 weeks then something like the pictures will happen. But that is no guarantee that it will cause this display problem.

A refresh of X or restart may sometimes clear the issue for a short period of time. So will reseeding the graphics chip. These are usually temprementaly and revert back to the original problem after a day or two.

We have been thinking it was a monitor issue, but when moved the monitors over to a windows machine using the same graphics card/dongle it will display perfectly on the windows computer. Or when moved the monitor from linux computer to linux computer the display will be clear on both computers.

I'm wonder if anyone else out there has experienced this issue?
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Old 02-22-11, 08:01 AM   #12
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Default Re: Green / Pink Flashing Pixels 195.36.15

I have the same issue with an HP LA2405 Monitor. This issue was missing with my old 19" Benq.

The same group of 5-10 pixels are blinking since two weeks when I changed to the new HP monitor. I do not see the blinking all the time. It aperas when there is increased activity - Some of the games and sometimes movies. I am running in a dual monitor mode (extended desktop on my Philips 42" TV using DVI to HDMI cable. The dots apera only on my primary display.

On some other forums I can see that this issue might be caused by a low quality cable so the first thing to do when I go to home today would be to replace my old Benq DVI with the HP one .
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