CPU frequency scaling issues

Oct 13, 2025 by talynt.org 43 views

Introduction

As a user of Kubuntu 24.04 on a 64-bit system, you may have encountered an issue where the scaling current frequency is low (~399 MHz) when the charger is plugged in. This can be a frustrating problem, especially if you're used to your system performing at its best. In this article, we'll delve into the possible causes of this issue and provide you with some potential solutions to get your system running at its optimal frequency.

Understanding the Issue

The scaling current frequency is a measure of the current CPU frequency, which is the rate at which the CPU executes instructions. This frequency is typically adjusted based on the system's workload and power consumption. However, when the charger is plugged in, the system may not be able to adjust the frequency to its optimal level, resulting in a lower than expected frequency.

Analyzing the Output

When you run the command cat /sys/bus/cpu/devices/cpu*/cpufreq/scaling_cur_freq, you may see an output similar to the following:

This output indicates that the current CPU frequency is around 399 MHz, which is lower than expected. This can be a sign of an issue with the system's power management or CPU frequency scaling.

Possible Causes

There are several possible causes of this issue, including:

Power management issues: The system's power management may not be functioning correctly, resulting in a lower than expected frequency.
CPU frequency scaling issues: The CPU frequency scaling may not be working correctly, resulting in a lower than expected frequency.
Hardware issues: There may be a hardware issue with the CPU or motherboard, resulting in a lower than expected frequency.

Troubleshooting Steps

To troubleshoot this issue, you can try the following steps:

Check the system's power management: You can check the system's power management by running the command cat /sys/class/power_supply/BAT*/capacity. This will give you an idea of the system's battery capacity and whether it's functioning correctly.
Check the CPU frequency scaling: You can check the CPU frequency scaling by running the command cat /sys/bus/cpu/devices/cpu*/cpufreq/scaling_cur_freq. This will give you an idea of the current CPU frequency and whether it's functioning correctly.
Check for hardware issues: You can check for hardware issues by running the command lspci -v and lscpu. This will give you an idea of the system's hardware configuration and whether there are any issues with the CPU or motherboard.

Solutions

Based on the possible causes and troubleshooting steps, here are some potential solutions to get your system running at its optimal frequency:

Update the system's power management: You can update the system's power management by running the command sudo apt update && sudo apt upgrade. This will ensure that the system's power management is up to date and functioning correctly.
Adjust the CPU frequency scaling: You can adjust the CPU frequency scaling by running the command sudo cpufreq-set -g performance. This will set the CPU frequency scaling to the performance governor, which will allow the system to adjust the frequency to its optimal level.
Check for hardware issues: You can check for hardware issues by running the command lspci -v and lscpu. This will give you an idea of the system's hardware configuration and whether there are any issues with the CPU or motherboard.

Conclusion

In conclusion, a scaling current frequency of ~399 MHz when the charger is plugged in can be a frustrating issue. However, by understanding the possible causes and troubleshooting steps, you can identify and resolve the issue. By updating the system's power management, adjusting the CPU frequency scaling, and checking for hardware issues, you can get your system running at its optimal frequency.

Additional Tips

Here are some additional tips to help you troubleshoot and resolve this issue:

Check the system's logs: You can check the system's logs by running the command sudo journalctl -u systemd-logind. This will give you an idea of any issues with the system's power management or CPU frequency scaling.
Check the system's BIOS: You can check the system's BIOS by running the command sudo dmidecode -s bios-version. This will give you an idea of the system's BIOS version and whether it's up to date.
Check for firmware updates: You can check for firmware updates by running the command sudo apt update && sudo apt upgrade. This will ensure that the system's firmware is up to date and functioning correctly.

References

[1] Kubuntu documentation
[2] CPU frequency scaling documentation
[3] Power management documentation
Scaling Cur Freq is Low (~399 MHz) when the Charger is Plugged In: Q&A ====================================================================

Q: What is the scaling current frequency, and why is it important?

A: The scaling current frequency is a measure of the current CPU frequency, which is the rate at which the CPU executes instructions. It's an important metric because it affects the system's performance, power consumption, and heat generation.

Q: Why is my scaling current frequency low (~399 MHz) when the charger is plugged in?

A: There are several possible reasons for this issue, including power management issues, CPU frequency scaling issues, and hardware issues. It's essential to troubleshoot and identify the root cause to resolve the issue.

Q: How can I check the system's power management?

A: You can check the system's power management by running the command cat /sys/class/power_supply/BAT*/capacity. This will give you an idea of the system's battery capacity and whether it's functioning correctly.

Q: How can I check the CPU frequency scaling?

A: You can check the CPU frequency scaling by running the command cat /sys/bus/cpu/devices/cpu*/cpufreq/scaling_cur_freq. This will give you an idea of the current CPU frequency and whether it's functioning correctly.

Q: What are some potential solutions to get my system running at its optimal frequency?

A: Some potential solutions include updating the system's power management, adjusting the CPU frequency scaling, and checking for hardware issues. You can also try checking the system's logs, BIOS, and firmware updates.

Q: How can I update the system's power management?

A: You can update the system's power management by running the command sudo apt update && sudo apt upgrade. This will ensure that the system's power management is up to date and functioning correctly.

Q: How can I adjust the CPU frequency scaling?

A: You can adjust the CPU frequency scaling by running the command sudo cpufreq-set -g performance. This will set the CPU frequency scaling to the performance governor, which will allow the system to adjust the frequency to its optimal level.

Q: What are some additional tips to help me troubleshoot and resolve this issue?

A: Some additional tips include checking the system's logs, BIOS, and firmware updates. You can also try running the command sudo dmidecode -s bios-version to check the system's BIOS version and whether it's up to date.

Q: Where can I find more information about power management and CPU frequency scaling?

A: You can find more information about power management and CPU frequency scaling in the Kubuntu documentation, CPU frequency scaling documentation, and power management documentation.

Q: What are some common issues that can cause a low scaling current frequency?

A: Some common issues that can cause a low scaling current frequency include power management issues, CPU frequency scaling issues, and hardware issues. It's essential to troubleshoot and identify the root cause to resolve the issue.

Q: How can I prevent a low scaling current frequency in the future?

A: To prevent a low scaling current frequency in the future, you can ensure that the system's power management and CPU frequency scaling are up to date and functioning correctly. You can also try checking the system's logs, BIOS, and firmware updates regularly.

Q: What are some best practices for maintaining a healthy and efficient system?

A: Some best practices for maintaining a healthy and efficient system include:

Regularly updating the system's power management and CPU frequency scaling
Checking the system's logs, BIOS, and firmware updates regularly
Ensuring that the system's hardware is functioning correctly
Avoiding overheating and overloading the system
Monitoring the system's performance and adjusting settings as needed