[BIOS BUG] Fan thermal control issues

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aw_
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[BIOS BUG] Fan thermal control issues

Post by aw_ »

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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Re: [BIOS BUG] Fan thermal control issues

Post by mad_ady »

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

Post by aw_ »

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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Re: [BIOS BUG] Fan thermal control issues

Post by mad_ady »

What bios version are you running?

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Re: [BIOS BUG] Fan thermal control issues

Post by aw_ »

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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Re: [BIOS BUG] Fan thermal control issues

Post by odroid »

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

Post by odroid »

The fan controller IC has its own external thermal sensors.
N2_Thermal.jpg
N2_Thermal.jpg (95.55 KiB) Viewed 1124 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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Re: [BIOS BUG] Fan thermal control issues

Post by spitefulmonkey »

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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