I'm having a problem with the last distributive of Ubuntu. The problem is that with an Intel DualCore E7500, 4GB of RAM DDR3-1600 and x32 bits type of OS with PAE enabled, I have not met performance issues, but when I have switched to AMD Athlon X2 245, 4GB of RAM DDR3-1600 and x64 bits type of OS, after this performance fell. Even at startup of Ubuntu without any active process, GUI is slow. I have disabled Detect Refresh Rate, Sync to V Blank in Compiz, but but without any success. It's the problem really in x64 version of Ubuntu or the problem is the Processor?
1) glxinfo | grep -i direct
direct rendering: Yes GL_EXT_copy_buffer, GL_EXT_copy_texture, GL_EXT_direct_state_access,
2) sudo lspci | grep VGA
01:05.0 VGA compatible controller: ATI Technologies Inc 760G [Radeon 3000]