intel driver gets slow as soon as I rotate on a 1920x1200 display

[Thomas Glanzmann]

Hello,
I just checked out Xorg from git and compiled it on Debian Etch. I have
a EIZO S2431W with a resolution of 1920x1200 attached to a Mac Mini with
a Intel 945GM[1]. As soon as I call "xrandr -o 1" I loose all my
accerlation. I can literally watch how the "ls -al" output of a full
screen xterm scrolles up. It takes several seconds to complete.  My
/etc/X11/xorg.conf is at [2] and my Xorg.log.0 at [3]. Has anyone a idea
what I did wrong or what I can do to improve the behaviour? Did I use
the right intel driver?

[1] Intel Corporation Mobile 945GM/GMS/940GML Express Integrated Graphics Controller (rev 03)
[2] http://wwwcip.informatik.uni-erlangen.de/~sithglan/xorg.conf
[3] http://wwwcip.informatik.uni-erlangen.de/~sithglan/Xorg.0.log

The following output pops up in Xorg.log.0 when I type in "xrandr -o 1":

(II) intel(0): I2C device "SDVOB DDC Bus:ddc2" registered at address 0xA0.
(II) intel(0): I2C device "SDVOB DDC Bus:ddc2" removed.
(II) intel(0): EDID vendor "ENC", prod id 6279
(II) intel(0): I2C device "SDVOB DDC Bus:ddc2" registered at address 0xA0.
(II) intel(0): I2C device "SDVOB DDC Bus:ddc2" removed.
(II) intel(0): EDID vendor "ENC", prod id 6279
(II) intel(0): fbc disabled on pipe a
(II) intel(0): fbc enabled on pipe a


The following output pops up in Xorg.log.0 when I switch back using "xrandr -o 0":

(II) intel(0): I2C device "SDVOB DDC Bus:ddc2" registered at address 0xA0.
(II) intel(0): I2C device "SDVOB DDC Bus:ddc2" removed.
(II) intel(0): EDID vendor "ENC", prod id 6279
(II) intel(0): I2C device "SDVOB DDC Bus:ddc2" registered at address 0xA0.
(II) intel(0): I2C device "SDVOB DDC Bus:ddc2" removed.
(II) intel(0): EDID vendor "ENC", prod id 6279
(II) intel(0): fbc disabled on pipe a
(II) intel(0): fbc enabled on pipe a

	Thomas