I run ubuntu 11.10 on a Dell inspiron N4050 which has an Intel Core i3 CPU.
After a time of inactivity sometimes few seconds, sometimes 2 or three miutes or even more CPU2 3 and 4 spike then go to zero and only CPU1 still works. when activity is resumed by moving the cursor for example all CPUs are put on.
I would like to post an image but since i'm new i couldn't.
I don't know if putting off the three last cores of the CPU is an option to reduce power consumption or something like that..