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I recently tried to boot my Kubuntu 12.04 LTS on my Sandy Bridge Laptop with i915.i915_enable_rc6=1, i915.i915_enable_fbc=1 and i915.lvds_downclock=1. I had some issues with 3D performance where somebody suggested using those options.

Since the resolution was not set correctly, I just tried it again with i915.i915_enable_rc6=1, i915.i915_enable_fbc=1. Then I rebooted and did not set any options manually, so everything should be reset. But since then, some KWin effects, especially wobbly windows does not work any more.

I also tried to boot some older kernel, but that did not have any effect.

How can I get it back to work?

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kwin will disable desktop effects when it detects issues with drivers or hardware.

To re-enable them you can go to KDE's system-settings. Or you may be able to just hit Alt+Shift+F12.

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Well, it does not re-enable wobbly windows. – Martin Ueding Dec 1 '12 at 18:44

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