Red Hat Bugzilla – Bug 846365
Dual head on intel mobile 945gm (not mirrored)
Last modified: 2012-08-23 10:59:49 EDT
Description of problem:
Connecting an external monitor has no effect. When attempting to turn the monitor on(in display settings) the system becomes extremely slow/unusable. Turning the monitor off returns the system to a usable state.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
The external works fine on it's own if I invoke Fn+F5. See full explanation of symptoms: http://lists.fedoraproject.org/pipermail/users/2012-July/422209.html
Yeah, well, i945's terrible like that. i915 and i945 have a limitation in their hardware acceleration where they can't work on surfaces that are more than 2048 pixels wide. Presumably enabling dualhead is causing you to exceed that limit, and then all your drawing hits software fallbacks.
*** This bug has been marked as a duplicate of bug 699705 ***
I don't agree that this is a duplicate. I've experienced the 2048 pixel and although this does still exist since I have that chipset the symptoms I was refering to are not those of bug 699705. In bug 699705 the monitor automatically switches on but in doing so renders the system unusable if the display is set to 2048 or more. To avoid that I had my display settings below that limitation to avoid those symptoms. My external monitor would not turn on.
Case in point I just updated to 3.5.2-3.fc17.i686kernel 3.5 and connecting an external monitor now works. I'm still stuck within 2048 horizontally but at this point I'll take what I can get ;) My workaround for this has always been to stack my monitors vertically. It's akward if you're accustom to having them the other way but it works!