BIOS Fan Curve Too Aggressive

BIOS Fan Curve Too Aggressive | Generated by AI

Home 2026.07

Good news — the system is thermally fine. The fan noise is a BIOS behavior issue, not a cooling problem. Here’s the diagnosis:

Temperatures (all cool):

CPU package: 38°C (max core 35°C)
GPU: 33°C, 11W, fan at 0% (passive)
NVMe: 39.9°C
Ambient/chassis: 27.8°C

No thermal reason for fans to be loud.

The problem: The system has a PWM fan controller (INTC1085:00 on Intel chipset) but the OS never exported the pwm0 channel — it’s at npwm=1 (1 fan header detected) but pwm0/ directory doesn’t exist. This means the OS isn’t driving the fans at all. They’re running at BIOS/UEFI default, which is typically 100% or a very aggressive curve. This is common on desktop boards where the BIOS handles fan control without handing it off to the OS.

lm-sensors found no fan speed sensors anywhere — the board’s super I/O isn’t exposing RPM readings either.

Likely cause: The machine just booted 3 minutes ago. The BIOS fan curve is set to aggressive (possibly full speed at all temps), and thermald is running in polling mode with no config file (/etc/thermald/thermal-conf.xml doesn’t exist), so it’s not doing anything useful.

Things you can try:

Enter BIOS/UEFI (usually Del/F2 at boot) and adjust the fan curve — set a silent/profile or manual curve. Since the OS can’t control fans, this is the place to fix it.
Check if the noise is actually the HDD — the 1.8TB WD20EZBX (7200RPM) at /mnt/data is a mechanical drive and makes audible seek/rotation noise. Unmount it temporarily to test if the noise stops.
If you want OS-level fan control, you’d need to export the PWM channel:
```
echo 0 | sudo tee /sys/devices/platform/INTC1085:00/pwm/pwmchip0/export
```
Then set duty cycle. But this is board-specific and might not work if the BIOS doesn’t allow OS fan control.
Create a thermald config at /etc/thermald/thermal-conf.xml to give it proper thermal policies, though this won’t help if the BIOS isn’t surfacing fan control to the OS.

The quickest fix: go into BIOS and set a silent fan profile. The system is cool enough to run fans at minimum speed.

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