I have here a rather old Thinkpad with a Mobility Radeon HD 3400 series card, having similar problems:

• The closed-source fglrx driver is almost unusable, due to flickering, glitches, etc with gnome-shell.




• The open-source radeon driver is working very nice, but the card gets too hot. Checking using cat /proc/acpi/ibm/thermal shows that the card heats up to > 90°C.

My solution:
- Use the open-source radeon-driver (accodring to the man-page your card is supported) and manually clock down the card: If it is not installed already, install it, the package is named 'xserver-xorg-video-radeon':

aptitude install xserver-xorg-video-radeon

Purge fglrx:

aptitude purge fgrlx

On the next start, X will automagically use the radeon driver. You can check this using 'lsmod | grep radon', you should see something like this:

root@XERXES3:~# lsmod | grep radeon

radeon               1015995  3 

ttm                    76805  1 radeon

drm_kms_helper         42558  1 radeon

drm                   236330  5 radeon,ttm,drm_kms_helper

i2c_algo_bit           13423  1 radeon

ensure that the fglrx driver is not loaded, 'lsmod | grep fglrx' should produce no output.

Check if your card is running at the highest speed too: 'cat /sys/kernel/debug/dri/0/radeon_pm_info' shows you the clock-speed of your card

root@XERXES3:~# cat /sys/kernel/debug/dri/0/radeon_pm_info 

default engine clock: 680000 kHz

current engine clock: 675000 kHz

default memory clock: 800000 kHz

current memory clock: 792000 kHz

voltage: 1200 mV

PCIE lanes: 16

Set the power-profile to something more reasonable:

echo "mid" > /sys/class/drm/card0/device/power_profile

Now check again the clock-speed of your card:

root@XERXES3:~# cat /sys/kernel/debug/dri/0/radeon_pm_info 

default engine clock: 680000 kHz

current engine clock: 297000 kHz

default memory clock: 800000 kHz

current memory clock: 405000 kHz

voltage: 900 mV

PCIE lanes: 16

It should show reduced clock-speeds and voltage.

That did the job for me. I'm now using gnome 3 for quite some time, things work very nice with Ubuntu. You might also be interested in this bug-report:

http://ati.cchtml.com/show_bug.cgi?id=99

It seems like ATI is having serious problems in providing a decent working linux-driver.

Also note, that this problem of "Radeon driver is clocking the card too hot" started to appear on my system with the introduction of KMS. It seems like the card is never switched to a reasonable power-profile, even if it is getting too hot.
Before KMS, I was able to use in Xorg.conf the options "dynamic clocks on" (or similar) and the card adjusted its speed properly.

ATM I'm just setting the power-profile to "mid" each time after booting (a script could do the job).

Hope this helps, cheers

Note, I forgot to mention one thing: If you have a system with switchable graphics (in my case a thinkpad T400 with a ati card and a ibm gfx-chip), you need to disable the 'switchable graphics' in the bios and manually set in the bios which card to use (Discrete graphics in my case to use the ati-card). If not, it might happen that both cards are "powered-up" and are running at top-speed, producing heat. Here is a lot of informations about this:

http://en.gentoo-wiki.com/wiki/Lenovo_ThinkPad_T400#Getting_graphics_to_work