vertical line of unresponsive pixels on thinkpad T420s

Mr. M

I'm having a strange issue on my thinkpad T420s that first started occurring a few weeks ago. I'm not sure if it a software bug or a hardware issue and I haven't found reports of similar problems, so I thought I would post here and see what you guys think.

So, basically there is a single vertical line of pixels that sometimes seem to get "stuck", i.e., the pixels don't update. The stuck pixels go away when I move a window over them, but they stay stuck when moving the mouse pointer over them. The later makes me think it may be a software problem, but I think it would be odd as I run a very common configuration (gentoo-sources, xf86-video-intel, KDE), so one would think that there should be reports of others having this problem. Also, the problem only seems to occur after a few sleep/resume cycles.

Has anyone ever seen something similar?

b0nafide · Apprentice Joined: 17 Feb 2008 Posts: 171 Location: ~/

My guess would be a bad LVDS cable or LCD screen. Try reseating the cable and check to make sure the jacket of the cable is not being pinched or worn away by it's path through the hinge of the laptop. Good luck.

chithanh · Posted: Sun Apr 13, 2014 7:11 pm Post subject:

This could also be bad video memory. As Intel graphics use shared memory, it might show up in memtest output.

If you suspect a software issue, you could try to switch between uxa, sna and glamor for 2D acceleration.

Mr. M · Posted: Thu Apr 24, 2014 6:37 pm Post subject:

I now think that it is either a driver or xorg bug. The problem only occurs after I attach an external 1920x1200 monitor using the display port, not sure why I didn't notice this before. Restarting xorg fixes the problem. I will do a test using the different acceleration modes.