What is my CPU speed?

Question

I need the CPU speed of my KVM host.

When I am using dmidecode, the result is the following :

sudo dmidecode | egrep "Max Speed|Current Speed"

Max Speed: 3100 MHz

Current Speed: 3100 MHz

Whereas, when I am using lscpu, the result is:

lscpu | grep "MHz".

CPU MHz: 1600.000

So, why there are two different values, and between the two, which is my actual CPU speed?

Additional :

When the /proc/cpuinfo file has the following result for the speed of the individual cores.

cat /proc/cpuinfo | grep "MHz"

cpu MHz : 1600.000

cpu MHz : 1600.000

cpu MHz : 1600.000

cpu MHz : 1600.000

Can anybody explain in details?

Answer 1

If you have cpufreq running, the driver which reduces CPU frequency during inactivity periods, you may take maximum frequency from it (in KHz):

$ cd /sys/devices/system/cpu/cpu1/
$ sudo cat cpufreq/cpuinfo_cur_freq
2363000
$ cat cpufreq/cpuinfo_max_freq
2600000

Note that 2,6 GHz is Intel "Turbo" frequency of my CPU, actual stock frequency is 1,7 MHz.

Answer 2

Your CPU has a rated speed of 3.1GHz. At the time you checked cpuinfo, it was running at 1.6GHz. When load is low, the CPU runs at a lower speed to save energy and keep itself cooler.