Make sure you report your issues in the bug tracker. If you have a Radeon card, "ubuntu-bug xserver-xorg-video-ati" is the best way to start filing a bug. Please also report how much video memory you have on your card.
First, check which acceleration you are using:
grep XAA /var/log/Xorg.0.log
grep EXA /var/log/Xorg.0.log
EXA has now replaced XAA as the default, except for cards with little memory. However there are some issues with XAA, so there are two things to try if your card runs XAA:
A. Disable RenderAccel, by creating an /etc/X11/xorg.conf with this:
Code:
Section "Device"
Identifier "my-radeon"
Driver "ati"
Option "RenderAccel" "off"
EndSection
B. Force the use of EXA instead:
Code:
Section "Device"
Identifier "my-radeon"
Driver "ati"
Option "AccelMethod" "EXA"
EndSection
One other thing to try for low-memory cards is to reduce the virtual screen size to what you are actually using:
Code:
Section "Device"
Identifier "my-radeon"
Driver "ati"
EndSection
Section "Screen"
Identifier "my-screen"
Device "my-radeon"
# DefaultColorDepth 16
SubSection "Display"
Virtual 1024 768
EndSubSection
EndSection
Change the Virtual parameters to your screen resolution, of course. Note that by further uncommenting the DefaultColorDepth line you will get fewer colors but even less memory is needed (depth 24 is default).
On the other hand, for AGP cards with decent amounts of video RAM, increasing the AGPSize might help. Run grep "GART aperture" /var/log/Xorg.0.log to see the default value.
Code:
Section "Device"
Identifier "my-radeon"
Driver "ati"
Option "AGPSize" "128"
EndSection
The number "128" has to be tuned for your hardware, try 16, 32, 64, 128 up to the amount of video RAM that you have. Higher numbers will reserve more system memory, so just set it as high as you need.
Finally, one can try KMS (Kernel mode-setting) which enables a video memory manager and DRI2 (for 3D rendering). This will be default in future releases, so this is where most development is focused. See https://wiki.ubuntu.com/X/RadeonKMS for how to try it.
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