I've got problems with my AMD (ATI) Radeon HD 5670 in Ubuntu 12.04 LTS (Precise Pangolin).

I had 2GB of RAM (DDR2, PC6400, 800MHz), I added another 2GB so now I have 4GB (2x2GB) and I'm not able to use fglrx drivers.

I've applied patch for new kernel http://phoronix.com/forums/showthrea...86-32-bit-arch and installed latest Catalyst 12.4 drivers succesfully without any errors according to WIKI pages http://wiki.cchtml.com/index.php/Ubu...TI.27s_site.29 but unfortunately after system restart I get black or violet screen and I'm not even able to switch to other virtual console with Ctrl+Alt+F1...F6. When I remove 2GB (only 2GB left) system starts normally and everything works fine.

It's not RAM issue, because I've got Windows 7 installed as well and it works fine, 4GB of memory are visible in the system. Besides when I installed Backtrack 5 which is based on Ubuntu 10.04 LTS, 12.4 catalyst drivers were working correctly with 4GB RAM inserted.

All installations were made on fresh and updated system. After I install drivers and execute
sudo amdconfig --initial -f
fglrxinfo output and xorg.conf (before this command there was no /etc/X11/xorg.conf) are as follows (right after installation and before system restart):
przemek@pc:~/catalyst12.4$ sudo amdconfig --initial -f
Uninitialised file found, configuring.
Using /etc/X11/xorg.conf
Saving back-up to /etc/X11/xorg.conf.original-1
przemek@pc:~/catalyst12.4$ cat /etc/X11/xorg.conf
Section "ServerLayout"
    Identifier     "aticonfig Layout"
    Screen      0  "aticonfig-Screen[0]-0" 0 0

Section "Module"

Section "Monitor"
    Identifier   "aticonfig-Monitor[0]-0"
    Option        "VendorName" "ATI Proprietary Driver"
    Option        "ModelName" "Generic Autodetecting Monitor"
    Option        "DPMS" "true"

Section "Device"
    Identifier  "aticonfig-Device[0]-0"
    Driver      "fglrx"
    BusID       "PCI:1:0:0"

Section "Screen"
    Identifier "aticonfig-Screen[0]-0"
    Device     "aticonfig-Device[0]-0"
    Monitor    "aticonfig-Monitor[0]-0"
    DefaultDepth     24
    SubSection "Display"
        Viewport   0 0
        Depth     24

przemek@pc:~/catalyst12.4$ fglrxinfo
display: :0  screen: 0
OpenGL vendor string: VMware, Inc.
OpenGL renderer string: Gallium 0.4 on llvmpipe (LLVM 0x300)
OpenGL version string: 1.4 (2.1 Mesa 8.0.2)

I moved xorg.conf file to see if it causes problems, but after
sudo mv /etc/X11/xorg.conf /etc/X11/xorg.conf.disabled
the problem was still present- black or violet screen.

After xorg.conf restoration
sudo mv /etc/X11/xorg.conf.disabled /etc/X11/xorg.conf
I tried to tune it according to wiki
sudo amdconfig --tls=0

sudo amdconfig --acpi-services=off
but without success...

Blacklisting radeon modules also did not help...
echo "blacklist radeon" | sudo tee -a /etc/modprobe.d/blacklist-radeon.conf
sudo depmod -a

Ofcourse when I remove 2GB RAM and leave 2GB- system boots normally and fglrxinfo looks very good:
przemek@pc:~$ fglrxinfo
display: :0  screen: 0
OpenGL vendor string: Advanced Micro Devices, Inc.
OpenGL renderer string: ATI Radeon HD 5670
OpenGL version string: 4.2.11631 Compatibility Profile Context

przemek@pc:~$ fgl_glxgears
Using GLX_SGIX_pbuffer
3178 frames in 5.0 seconds = 635.600 FPS
4172 frames in 5.0 seconds = 834.400 FPS
4163 frames in 5.0 seconds = 832.600 FPS
4153 frames in 5.0 seconds = 830.600 FPS
4165 frames in 5.0 seconds = 833.000 FPS
4152 frames in 5.0 seconds = 830.400 FPS
4141 frames in 5.0 seconds = 828.200 FPS
4160 frames in 5.0 seconds = 832.000 FPS
4162 frames in 5.0 seconds = 832.400 FPS
Problem is present only when 4GB are inserted... I borrowed 1GB of RAM and tested configuration with 3GB and it was working fine!

Used kernel supports 4GB of RAM (visible after free -m when fglrx drivers are not installed)
przemek@pc:~$ uname -r
The same situation is with fglrx drivers from repos...

What kind of logs can I check? Can anyone help me with this issue?

Looking forward,

P.S. I tried also 12.6 Beta version of catalyst drivers, mentioned patch was not need to successfully generate packages, but after installation situation is still the same- black or violet screen when 4GB are inserted...