On my debian-linux system, with a core i7 920 , each time I resume after the command "pm-suspend" (suspend to RAM), mutlithreading capabilities almost disappear. More specifically, two distinct programs can use 2 distinct cores at full rate, but a single program is limited to only one core (for one instance of a multithreaded program as well as multiple instances of a monothreaded program, e.g. "make -j 4" for gcc). So I end up rebooting the system. Any help appreciated!
See this debian bug. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=580901
Having the same pain in the butt with this bug on i7, so maybe I should switch to something more up-to-date than debian-stable. This is the first problem after several months of running the distro, so I think it's still not that much worth the effort though. More details than linked before available here: https://bugzilla.kernel.org/show_bug.cgi?id=15559
UPD: oh, and there's a workaround which seems to bring some of my cores back to life:
/sys/devices/system/cpu# for AA in `seq 2 1 7` ; do echo "0" > cpu$AA/online ; done; /sys/devices/system/cpu# for AA in `seq 2 1 7` ; do echo "1" > cpu$AA/online ; done;