Subject: Jetson Orin Showing Only 4 CPU Cores Instead of 8 - Hardware Detection Issue

[Seven0]

Hardware and Software Environment:

• Device: Jetson Orin (specific model to be confirmed)

• JetPack Version: [Please specify your JetPack version]

• Kernel: Linux 5.10.104

• nproc output: 4

• lscpu: Shows only 4 cores (0-3 online)

Problem Description:

My Jetson Orin device is only detecting 4 CPU cores instead of the expected 8 cores. The system seems to have hardware support for 8 cores based on nvpmodel configuration, but only 4 cores are actually available to the system.

Detailed Symptoms:

1. System Reports Only 4 Cores:

   $ nproc
   4
   
   $ lscpu | grep -E "CPU\(s\)|On-line"
   CPU(s):                          4
   On-line CPU(s) list:             0-3
   

2. nvpmodel Shows 8-Core Configuration:

   • Current mode: MODE_30W (should enable all 8 cores)

   • nvpmodel -p --verbose shows configuration for CORE_0 to CORE_7

   • However, getting errors accessing CPU4-CPU7 device files

3. Error Messages:

   NVPM ERROR: Error opening /sys/devices/system/cpu/cpu4/online: 2
   NVPM ERROR: Error opening /sys/devices/system/cpu/cpu5/online: 2
   NVPM ERROR: Error opening /sys/devices/system/cpu/cpu6/online: 2
   NVPM ERROR: Error opening /sys/devices/system/cpu/cpu7/online: 2
   

Diagnostic Information:

CPU Topology:

$ cat /sys/devices/system/cpu/possible
0-3

$ cat /sys/devices/system/cpu/present  
0-3

Physical CPU Devices:

$ ls /sys/devices/system/cpu/ | grep "^cpu[0-9]" | sort -V
cpu0
cpu1
cpu2
cpu3

What I’ve Tried:

1. Power Mode Changes:

   • Switched between different nvpmodel modes (0, 1, 2, 3)

   • All modes show the same 4-core limitation

2. Manual CPU Activation:

   • Attempted to manually enable cores via /sys/devices/system/cpu/cpuX/online

   • Device files for cpu4-cpu7 don’t exist

3. Kernel Parameter Check:

   • No maxcpus limitation in /proc/cmdline

   • No apparent boot-time restrictions

Questions:

1. Is this a known issue with certain Jetson Orin variants?

2. Could this be a device tree or kernel configuration problem?

3. Are there specific firmware updates needed for proper 8-core detection?

4. How can I verify the actual hardware capabilities of my device?

Additional Information:

• The device seems to be running well otherwise

• GPU and other components appear functional

• No obvious hardware damage or issues

Any guidance on diagnosing and resolving this core detection issue would be greatly appreciated!

[Seven0]

After I updated this, when I refreshed the ORIN, this situation occurred. Without updating this compressed package, the ORIN of JetPack5.0.2 version cannot be refreshed

[kayccc]

That seems not related with PCN, and the JetPAck 5.0.2 is too old, could you upgrad to the newer JetPack? Thanks

[Seven0]

I tried JetPack 5.1.2 and it shows the correct number of CPU cores, but we’ve made many modifications on JetPack 5.0.2 and cannot switch to JetPack 5.1.2 for now. Could you please help solve this issue?Thanks.

[kayccc]

We have a patch - “Patch which fixes an issue where less than 8 CPU cores was being detected on some Jetson AGX Orin 32GB production module“ for JP5.0.2/R35.1, please find it at Jetson Linux 35.1 | NVIDIA Developer to apply on your SW to see if able to fix this problem. Thanks

[Seven0]

Thanks for the patch! The CPU core issue is now fixed and everything is working properly.

[kayccc]

Glad to know issue fixed, next time you can visit that release page first, we usually put some critical issues patched there. Thanks

[Seven0]

Ok. Thank you.