How to fix cpu being throttled to 800 MHz on Dell Precision laptop?

Cerin

4/19/24, 4:36 PM

How would you get your CPU to reach the maximum frequency when it's being throttled to 800 MHz?

After upgrading my Ubuntu distro a few months ago, on a Dell Precision 5520 laptop, I noticed it became very slow. Then I noticed I hadn't heard my fans come in a while.

I went through all the diagnostic steps in this similar question, but that only helped me confirm that maximum CPU frequency should be 3.800000 GHz, and none of the commands to forcibly increase the frequency did anything.

I thought that maybe my fans were obstructed, and couldn't turn on, so the chips safety mechanisms were just forcibly slowing it down to prevent overheating. So I opened up my laptop, vacuumed out a little dust. But that didn't change anything.

I then followed this guide to enable manually turning my fans on and off. That allowed me to successfully activate my fans by running i8kfan 2 2. Unfortunately, that has no effect on my CPU frequency, which stays stuck at 800 MHz. Trying to force my CPU to run at a higher clock speed by running echo 3800000 | sudo tee /sys/devices/system/cpu/cpu3/cpufreq/scaling_max_freq has no effect.

My is my CPU being throttled?

For reference, the output of sensors is:

ath10k_hwmon-pci-0100
Adapter: PCI adapter
temp1:        +48.0°C  

dell_smm-isa-0000
Adapter: ISA adapter
Processor Fan: 4890 RPM
Video Fan:     4902 RPM
CPU:            +33.0°C  
Ambient:        +30.0°C  
Ambient:        +31.0°C  
Other:          +35.0°C  
Ambient:        +32.0°C  
Ambient:        +29.0°C  
Ambient:        +31.0°C  
SODIMM:         +33.0°C  

BAT0-acpi-0
Adapter: ACPI interface
in0:          12.48 V  
curr1:       1000.00 uA 

coretemp-isa-0000
Adapter: ISA adapter
Package id 0:  +34.0°C  (high = +100.0°C, crit = +100.0°C)
Core 0:        +33.0°C  (high = +100.0°C, crit = +100.0°C)
Core 1:        +34.0°C  (high = +100.0°C, crit = +100.0°C)
Core 2:        +32.0°C  (high = +100.0°C, crit = +100.0°C)
Core 3:        +32.0°C  (high = +100.0°C, crit = +100.0°C)

pch_skylake-virtual-0
Adapter: Virtual device
temp1:        +40.5°C  

nvme-pci-0300
Adapter: PCI adapter
Composite:    +33.9°C  (low  = -273.1°C, high = +82.8°C)
                       (crit = +84.8°C)
Sensor 1:     +33.9°C  (low  = -273.1°C, high = +65261.8°C)
Sensor 2:     +39.9°C  (low  = -273.1°C, high = +65261.8°C)

acpitz-acpi-0
Adapter: ACPI interface
temp1:        +25.0°C  (crit = +107.0°C)

If I'm reading that correctly, then the system knows the fans are on, and the CPU temperature sensors are working and showing the CPU temps are well below high levels, much less critical. So there's no reason why the CPU frequency should be stuck at 800 MHz, as shown by lscpu and other utilities.

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Nmath

4/19/24, 5:10 PM

Idle temps are not very useful if you're trying to determine if your system is thermal throttling. You need to look at the temps under a stress test.

Cerin

4/19/24, 5:12 PM

@Nmath Does Linux throttle the CPU based on the hypothetical future load it thinks it's going to have, or the load it currently has?

Nmath

4/19/24, 5:20 PM

Neither. Your motherboard firmware usually controls thermal throttling.

Doug Smythies

4/19/24, 6:00 PM

What is your processor make and model? do `grep "model name" /proc/cpuinfo`. See also [here](https://askubuntu.com/questions/1461903/ubuntu-22-04-1-throttling-cpu-from-4000mhz-to-400mhz-1000mhz-even-under-high-loa)

codlord

4/19/24, 6:40 PM

I had an issue recently which turned out to be the hardware PROCHOT bit was set and CPU was throttled, see here for details of how to diagnose/test to see if it's the same for you: https://askubuntu.com/questions/1446577

Elon Musk

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