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10:25 - Debian/X.org notes - X behavior changes in experimental

Apart from interesting features such as DRI2, KMS or input-hotplug, there are some minor changes in X in experimental that actually appear to disturb many users.

The first one is that Ctrl-Alt-Backspace does not kill X anymore. There is no easy consensus here, but many people were annoyed of killing X by mistake, so it's disabled by default now. To reenable it, add to the ServerFlags section of your xorg.conf:

        Option "DontZap" "off"

Another one is the background during X startup. Say goodbye to the old well-known grey background. Now you get a black background by default. To revert to the old behavior, pass -retro on the server command line (for instance in /etc/X11/xinit/xserverrc). Note that this option also reenables Ctrl-Alt-Backspace killing the server.

Finally, you might also see glxgears reporting very low frame rates (60) on some hardware. Well, please remember that it is not a benchmark, the output basically means nothing. This is why some distros even removed the fps output by default. The thing is that recent DRM stacks will just synchronize frame rendering on vertical blanks (can anybody here see 1000fps with human eye?). So if you have a 60Hz refresh rate, glxgears will report 60fps, that's it. But it has nothing to do with DRI or 3D being slow. Please try some relevant 3D programs or benchmarks before complaining :)