topic Re: CPU Frequency in Mobile and Desktop Processors

CPU Frequency

SoksonJr — Sat, 26 Mar 2022 13:42:22 GMT

Hello,

I am doing a project that requires me to undervolt my system and to do this, I have to reduce the frequency of my CPU. I have a script that should do this. However, I do usually get an "error setting cpu: 0" when I try use this script. I have attached a screenshot to show this.

After doing some troubleshooting on my own, I realized that the acpi driver or intel p-state driver is responsible for frequency control of the CPU. When I ran "cpupower frequency-info | grep driver", the response I got was "no or unknown cpu freq driver is active on this CPU". Please is there something I'm missing?

I'm using an Ubuntu 20.04 system and my processor name is Intel 3.1GHz dual-core Core i5 - 7267U.

Thanks,

Osoko.

Re: CPU Frequency

n_scott_pearson — Tue, 29 Mar 2022 04:17:48 GMT

If the microcode in your BIOS is up to date, then support for undervolting has been disabled. This was done to mitigate the Plundervolt! vulnerability. For more information, see articles Plundervolt! A new Intel Processor ‘undervolting’ Vulnerability and What is Plundervolt! and How Does it Work?.

Sorry,

...S

Re: CPU Frequency

SoksonJr — Thu, 31 Mar 2022 21:03:31 GMT

Hi Scott,

Thank you for your response. I am actually trying to replicate the plundervolt attack on my system. I was able to control my CPU clock speed by downloading a bootable ubuntu disk on my system instead of using a virtualized environment like virtual box. However, I still could not perform the undervolting.

Please how can I check if the microcode in my BIOS is up to date?

Re: CPU Frequency

n_scott_pearson — Fri, 01 Apr 2022 01:32:13 GMT

Check the Release Notes for the BIOS. It should document the microcode being included.
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Re: CPU Frequency

SoksonJr — Sat, 02 Apr 2022 23:18:48 GMT

Hi Scott,

The microcode version currently running on my processor is 0xea. From what I'm seeing, I believe the micocode has been updated. I have attached a screenshot to this message. Please check it out. Thank you.

Osoko.

Re: CPU Frequency

n_scott_pearson — Sun, 03 Apr 2022 00:42:25 GMT

That's new enough that it likely has the workaround.
...S

Re: CPU Frequency

SoksonJr — Sun, 03 Apr 2022 01:33:03 GMT

Oh wow. Thank you for your help. I really appreciate.