ok found where the problem was. xorg (wrongly) chose radeonhd driver instead of radeon one :)
i solved explicity choosing Driver "radeon" in xorg.conf lspci: 01:00.0 VGA compatible controller: ATI Technologies Inc RV530 [Radeon X1600] 01:00.1 Display controller: ATI Technologies Inc RV530 [Radeon X1600] (Secondary) -- [intrepid] high cpu usage after boot https://bugs.launchpad.net/bugs/256188 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
