00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor
Graphics Controller (rev 09)
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI]
Wimbledon XT [Radeon HD 7970M] (rev ff)

I'm on latest mesa git and xf86-video-intel-git and it has been happening for a
while.

Here is a video: https://www.youtube.com/watch?v=al_gLzInYq0
sorry about the shaking and bad quality but as you can see in the video, the
effect vanishes when a screen recording application is running.

It also only happens with compositing, (both xrender and opengl compositing)
and vanishes when compositing is disabled.

I didn't think much about it, because it only affected glxgears and no other
application, but then I tested zetrix in wine:
http://www.download-central.ws/Win32/Tetris/ZetriX/ and I saw the same effect.
It doesn't work right anyway, i.e. fonts don't show, but the background
animation has these line artifacts too.

And then I have no idea if this is the correct place here at radeonsi.