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MKang3
Beginner
903 Views

what's the difference between p-state and speedstep ?

In my understanding, they are both adjusting voltage and freq for power efficiency.

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10 Replies
n_scott_pearson
Super User Retired Employee
432 Views

They're synonymous. See here for more information: https://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface.

...S

MKang3
Beginner
432 Views

https://wiki.archlinux.org/index.php/CPU_frequency_scaling

 

intel_pstate This driver implements a scaling driver with an internal governor for Intel Core (Sandy Bridge and newer) processors.

acpi-cpufreq CPUFreq driver which utilizes the ACPI Processor Performance States. This driver also supports the Intel Enhanced SpeedStep (previously supported by the deprecated speedstep-centrino module).

 

It looks they use different drivers.

 

When p-state enabled, speedstep will be disabled ?

n_scott_pearson
Super User Retired Employee
432 Views

No, both should be active and working together.

MKang3
Beginner
432 Views

If both will be enabled, OS should provide target speed/freq to speedstep( CPU MSR ), and p-state will also working it's own target speed/freq, isn't it ?

Oscar_A_Intel1
Employee
432 Views

Hello MKang3, Thank you for posting on the Intel Community. Correct, both technologies are related to the CPU frequency and its power consumption, however, both work separately . The Intel SpeedStep® Technology allows the system to dynamically adjust the processor voltage and core frequency, decreasing the average power consumption and heat production to avoid overheating issues. If you would like to know more about this technology, please visit this article with the information. https://www.intel.com/content/www/us/en/support/articles/000007073/processors.html While the CPU P-states represent voltage-frequency control states defined as performance states. The voltage and clocks that drive circuits are increased or decreased in response to a workload. Hope this helps! Oscar A. Intel Customer Support Technician Under Contract to Intel Corporation
Oscar_A_Intel1
Employee
432 Views

Hello MKang3, I'd like to know if you found the information provided useful? Best regards, Oscar A. Intel Customer Support Technician Under Contract to Intel Corporation
MKang3
Beginner
432 Views

Hi Oscar,

 

Sorry, I am not very clear.

Do you mean these two features will work separately at the same time? ( both enabled )

or only one can be enabled at the same time ?

 

In my understanding, speedstep also depends on OS workload.

http://download.intel.com/design/network/papers/30117401.pdf

 

In my understanding, they should conflict if work at the same time together.

 

Thanks.

Mark Kang.

Oscar_A_Intel1
Employee
432 Views

Hello MKang3, No problem. They won't have any issues if work at the same time since they work separately to perform different functions. The Intel SpeedStep® Technology is more used in laptop computers for example, since it helps saving power consumption (battery). You can disable or enable this option in the BIOS if supported. The P-States depends more on the workload and the control of frequency and voltage needed by the processor. Regards, Oscar A. Intel Customer Support Technician Under Contract to Intel Corporation
MKang3
Beginner
432 Views

Hi Oscar,

 

I got it, thank you for your feedback.

 

Mark Kang.

Oscar_A_Intel1
Employee
432 Views

Hello MKang3, You're very welcome. Please contact us if you have any other questions. Regards, Oscar A. Intel Customer Support Technician Under Contract to Intel Corporation
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