CPU Frequency Changing for Intel CPU

[Kevin]

Hi all,

I got a question when I changed the Intel CPU frequency for applications performance. When I changed the CPU frequency by 'cpupower'(which is a command line tool to change the cpu frequency) from 2300MHz(which is the maximum frequency in the Intel CPU) to 2301MHz, the execution time and power consumption of an application are totally different. The power consumption of frequency setting 2301MHz is 1.5 times than 2300MHz and the execution time is around 1.2 times than it. 

My question is: What's the meaning from changing a Intel CPU frequency from 2300MHz to 2301MHz(in this case)? Does that mean the 1MHz is specific to change the voltage/power capping/CPU mode/any other changes in Intel CPU?

Application
core frequency	Exe time(s)	Energy(J)	Average power (w)
2300MHz	20.0	2916	146
2301MHz	16.7	3648	218

I am really appreciated if someone can help me.

Thank you so much! 

Regards,

Kevin

[McCalpinJohn · Accepted solution]

The notation that adds "01" MHz is commonly used in CPU frequency utilities to to mean "request the maximum possible Turbo frequency".

Depending on your processor and system and BIOS and OS and whatever else is running on the system, the maximum Turbo frequency could be quite a bit higher than the 2300 MHz "base" frequency.   

As an example, the Intel Core i5-6350HQ has a nominal frequency of 2.3 GHz, but a maximum Turbo frequency of 3.2 GHz.   This could easily account for the reduced run time and increased power consumption in your results.

[Kevin]

Hi John,

Got it. Thank you so much for your quickly reply. 

Regards,

Kevin