Ubuntu – CPU frequency control

Actually as you are running all 4 cores, the maximum frequency won't be achieved as specified. Intel specifies maximum turbo frequency for a single running core.

There are different maximum frequencies achieved for 1 active core and for 4 active cores (to prevent going over TDP) http://www.cpu-world.com/CPUs/Core_i5/Intel-Core%20i5-3210M%20(BGA)%20Mobile%20processor.html

e.g. thus you are getting around 2.9 ghz rather than 3.1

if you look in i7z there is a line specifying //// max multiplier achieved with 1/2/3/4 core. You cannot go above those multipliers if more than some number of cores are active.

also, inactive core need to be in C3 or higher states to allow the active core(s) to get into higher turbo levels.

After more looking around, I've found two relevant issues on the kernel bugtracker that describe the same symptoms I'm experiencing. This one is marked as fixed, but this other one is new, with people reporting it's not yet fixed.

There seems to be something going on with putting the computer to sleep. The CPU runs normally, i.e. at low frequencies while idle, just after a reboot, but is stuck to high frequencies after waking up from sleep. After a fresh reboot, my frequencies looks like this (compare to what's posted in the question):

$ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq
1588875
800062
800062
800062
928500
2112937
800250
1911750

I guess for now we just have to wait until this is fixed.