When I try newest drivers intel-2.7.99 with card intel 945GM and I use parameter Virtual more than 2048*2048 in xorg.conf whole desktop is extremely slow. But when is the Virtual less than 2048^2 I get glxgears 380 but when it is bigger glxgears is ~5fps !!! and all graphic was unusable. This problem is only with newest drivers and when I use parameter virtual to be able to extent desktop to the second monitor. There are no errors in Xorg log connected to this except that DRI is not supported for >2048^2. I can get some more info but I don't know what would help you.
You don't get DRI acceleration if you set >2048 on pre-965. > This problem is only with newest drivers I'm interested to know which "old" driver version works for you?
I'm was using 2.6.1 because with drivers 2.6.3 - 2.7.1 the video didn't work (http://bugs.freedesktop.org/show_bug.cgi?id=21820), but UXA works fine with 2.7.1. I don't use UXA with old drivers but XAA, it works best for me with all drivers <2.6.3. I know that DRI will newer work, but still the drivers should be faster than 5fps. The new drivers I used are called xf86-video-intel-2.7.99.901 in gentoo portage.
so it's said to be a regression from 2.7.1 to 2.7.99.901, both with UXA.
I forgot to write that the dualhead didn't work with the newest drivers. It can only clone the screen but with drivers >2.7.1 I can't get dualhead work. So it is slow and the dualhead doesn't work. I also check the version from git://anongit.freedesktop.org/git/xorg/driver/xf86-video-intel and the problem is the same.
I expect people should meet bug#21190 with >2.7.1 as UXA enabled.
#21190 has been fixed for 945
2D performance should be fine for large (>2048) frame buffers. With DRI2, 3D performance should be acceptable on large frame buffers as long as the window is not larger than 2048 pixels. These are hardware limitations. 2D performance was broken, and fixed along with 21190, so I'm marking this bug fixed as well.
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