How to Set CPU Core Clock to Maximum on Nvidia Jetson Orin Nano

Issue Overview

Users of the Nvidia Jetson Orin Nano development board are seeking a way to set the clock speed of a specific CPU core to its maximum frequency. The issue arises in projects requiring dedicated CPU processing power, where the default behavior of dynamic clock speed adjustment based on load is undesirable. Users have successfully isolated a CPU core from the Linux system to run their own process or thread, but they want to maintain a constant maximum clock speed for that core, regardless of the workload.

Possible Causes

1. Default Power Management Settings: The Jetson Orin Nano’s default configuration likely includes power-saving features that dynamically adjust CPU clock speeds based on workload to optimize energy consumption.

2. Lack of User-Accessible Controls: The system may not provide readily available user controls for manually setting individual core clock speeds.

3. Operating System Interference: The Linux operating system’s default scheduler and power management policies might be overriding attempts to set a fixed clock speed for a specific core.

4. Hardware Limitations: There may be hardware-level constraints or thermal considerations that prevent setting a constant maximum clock speed for extended periods.

Troubleshooting Steps, Solutions & Fixes

1. Consult Official Documentation:
   Refer to the Jetson Linux Developer Guide for Jetson Orin Nano Series, specifically the section on power management and CPU frequency control. This documentation likely contains detailed information on how to modify CPU clock settings.

2. Use NVIDIA Jetson Clocks Tool:
   The Jetson platform typically includes a utility called jetson_clocks that can be used to set the system to maximum performance mode. Try running the following command in the terminal:

   sudo jetson_clocks
   

   This command sets all hardware clocks to their maximum frequencies.

3. Modify CPU Governor Settings:
   Change the CPU governor to "performance" mode for the specific core you want to run at maximum frequency. Use the following commands:

   sudo cpufreq-set -g performance -c [core_number]
   

   Replace [core_number] with the number of the core you’ve isolated.

4. Use CPU Frequency Scaling Tools:
   Install and use cpufrequtils to manually set the frequency of the specific core:

   sudo apt-get install cpufrequtils
   sudo cpufreq-set -f [max_frequency] -c [core_number]
   

   Replace [max_frequency] with the maximum frequency supported by your CPU core and [core_number] with the isolated core number.

5. Modify NVIDIA Power Mode:
   Use the NVIDIA-specific power mode setting to force maximum performance:

   sudo nvpmodel -m 0
   

   This sets the power mode to MAXN, which typically corresponds to maximum performance.

6. Check Thermal Throttling:
   Ensure that thermal throttling is not causing the clock speed to fluctuate. Monitor temperatures and consider improving cooling if necessary.

7. Kernel Parameter Modification:
   Add kernel boot parameters to disable CPU frequency scaling. Edit the /boot/extlinux/extlinux.conf file and add the following to the APPEND line:

   isolcpus=[core_number] nohz_full=[core_number] rcu_nocbs=[core_number] maxcpus=[total_cores]
   

   Replace [core_number] with your isolated core and [total_cores] with the total number of cores minus one.

8. Custom Kernel Module:
   As a more advanced solution, consider developing a custom kernel module that overrides the default frequency scaling behavior for the specific core.

9. BIOS/UEFI Settings:
   If accessible, check the BIOS/UEFI settings for any options related to CPU performance or power management that could be affecting clock speeds.

Remember to thoroughly test your system after making these changes, as running a CPU core at maximum frequency constantly can increase power consumption and heat generation. Ensure proper cooling and power delivery to maintain system stability.