[BIOS BUG] Fan thermal control issues

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aw_
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[BIOS BUG] Fan thermal control issues

Unread post by aw_ » Sun Jul 28, 2019 10:28 pm

If I set the following for my fan control parameters:

* low: 50C/800rpm
* middle: 60C/1200rpm
* high: 70C/1600rpm

Why is it that the fan only turns on ~84C and turns of ~82C? I expect with the above settings that the fan should run any time the system is above 50C, with increasing velocity the warmer the system gets. That is not what I observe. I think this is a BIOS bug. I'd also expect on a system like this that the upper fan control temperature should be extended to 80 or 90C rather than capped at 70C as it is now. Thanks.

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mad_ady
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Re: [BIOS BUG] Fan thermal control issues

Unread post by mad_ady » Sun Jul 28, 2019 11:46 pm

I too noticed that the fan is not coupled to the reported cpu temperature. The system has an extra temperature sensor on the motherboard (visible via lm-sensors) that triggers the fan. When the board is inside the case it's easier to trigger.

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Re: [BIOS BUG] Fan thermal control issues

Unread post by aw_ » Mon Jul 29, 2019 12:59 am

I see the ACPI temperature sensor as well as the per-core temperature in lm-sensors. Both average to similar values, though the fan does seem more tied to the ACPI temperature rather than the per-core temperatures, where the latter can change vary rapidly. It's the ACPI temperature ranges that I'm reporting above where the fan only comes on at ~84C and turns back off at ~82C.

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mad_ady
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Re: [BIOS BUG] Fan thermal control issues

Unread post by mad_ady » Mon Jul 29, 2019 2:33 am

What bios version are you running?

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Re: [BIOS BUG] Fan thermal control issues

Unread post by aw_ » Mon Jul 29, 2019 4:12 am

mad_ady wrote:
Mon Jul 29, 2019 2:33 am
What bios version are you running?
1.05

This is a Rev-B board that was only shipped a few weeks ago, with the latest BIOS already installed.

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odroid
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Re: [BIOS BUG] Fan thermal control issues

Unread post by odroid » Mon Jul 29, 2019 9:29 am

We will check which thermal sensor is coupled with the fan speed in the BIOS.

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Re: [BIOS BUG] Fan thermal control issues

Unread post by odroid » Tue Jul 30, 2019 4:42 pm

The fan controller IC has its own external thermal sensors.
N2_Thermal.jpg
N2_Thermal.jpg (95.55 KiB) Viewed 270 times
The sensors are placed near the CPU.
But the measured temperature from the sensor is much lower (around 15~25°C) than SoC inside.
So this issue might not be fixed logically soon.
Anyway, we will try to find a workaround.

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spitefulmonkey
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Re: [BIOS BUG] Fan thermal control issues

Unread post by spitefulmonkey » Wed Aug 14, 2019 3:06 pm

That is a lot of thermal paste :)

Could a thermal pad be placed over the sensor to make contact with the heatsink for a better cpu reading?

Or last thought, couldn't you simply use a python script to read the actual cpu temp and control the fans pwm wire via gpio. I've seen raspberry pi's doing this. That would give accurate fan control once the script was running and full speed until it is. https://www.raspberrypi.org/forums/view ... hp?t=84641

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