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u666sa

Member

Registered: 2020-08-01

Posts: 70

intel_pstate CPU scaling down to 800

My CPU spec https://ark.intel.com/content/www/us/en … 0-ghz.html
says 1.1GHz up to 2.8GHz, so 1.1 is minimum.

However, it scales down to 800 MHz.

I made it via script so that it sets minimum to 1100000 at boot, and I wonder if what I did actually matters?

I mean, valid question, there is no 800 MHz in CPU spec, minimum freq is 1.1GHz? Or am I missing some information?

Another thing. Setting governor to performance also scales CPU, it does not stay up at 2.8GHz all the time. Setting upper and lower limit to 2.8GHz does not work. Anyway to make it so that it is always at 2.8GHz? There are no other governors available with intel_pstate. btw. I want it to stay at 2.8 when on ac power.

Last edited by u666sa (2022-10-14 04:24:50)

stanczew

Member

Registered: 2021-03-02

Posts: 114

Re: intel_pstate CPU scaling down to 800

Read the descriptions on the linked page; 1.1 GHz is the base frequency, not the minimum:
"The processor base frequency is the operating point where TDP is defined."
The CPU can (and normally will) regulate itself to go below the base frequency, otherwise it would constantly consume power equal to TDP.

I made it via script so that it sets minimum to 1100000 at boot, and I wonder if what I did actually matters?

Today's CPUs are a lot better at figuring out how they should work than humans using them. Don't do things like that, let the CPU do its work.

Another thing. Setting governor to performance also scales CPU, it does not stay up at 2.8GHz all the time. Setting upper and lower limit to 2.8GHz does not work. Anyway to make it so that it is always at 2.8GHz? There are no other governors available with intel_pstate. btw. I want it to stay at 2.8 when on ac power.

2.8 GHz is the burst frequency:
"Burst frequency is the maximum single core frequency at which the processor is capable of operating."
It's the highest frequency a single core can achieve with the CPU being below TDP. If all cores were at 2.8 GHz, then power consumption would go way beyond TDP, and the CPU would get throttled… to around 1.1 GHz (i.e. base frequency)
There is no way to make the CPU stay at burst frequency, other than overclocking / manually changing power limits – but then you risk thermal issues (TDP limit is there for a reason). A 6 W TDP CPU just doesn't have the capability to maintain such frequency. Max you can do is force it to base frequency and disable scaling (so that it always stays at 1.1, occasionally bursting higher when needed and possible).