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102248 deseven 2025-07-08 21:12:40 1 
# Power Mode and Fan Control
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### Problem
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No fan and power mode control is available is available for Linux or Windows on Sixunited's AXB35 board.
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### Solution for Linux
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There is a [ec-su_axb35-linux kernel module](https://github.com/cmetz/ec-su_axb35-linux) written by Christoph Metz.
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It allows you to:
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- read current fan speeds and modes
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- switch modes of each of the three available fans
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- control fan speed in `fixed` mode
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- control fan speed with custom curves in `curve` mode
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- read current power mode
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- change current power mode
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- read current APU temperature
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#### Generic Installation
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1. Install module building dependencies (depends on your distro, on debian/ubuntu install `build-essential` and `linux-headers-$(uname -r)` packages).
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2. Clone the repo with `git clone https://github.com/cmetz/ec-su_axb35-linux.git`.
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3. Build and install the module with `cd ec-su_axb35-linux && sudo make install`.
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4. Try loading the module with `modprobe ec_su_axb35` and check your `dmesg` afterwards. You should see the `Sixunited AXB35-02 EC driver loaded` message.
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5. Run `scripts/info.sh` and check that all information is there.
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6. Run `scripts/test_fan_mode_fixed.sh`, it should test your fans on all 6 fixed levels.
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7. If everything is good, you can make the module automatically load on system boot with `sudo echo ec_su_axb35 >> /etc/modules`. If it says "permission denied", drop into root console with `su` or `sudo su -` and try again.
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#### Usage
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Reading and writing all of the parameters happens through sysfs with `/sys/class/ec_su_axb35` path. You can find detailed information in [the repo's readme file](https://github.com/cmetz/ec-su_axb35-linux/blob/main/README.md).
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Some examples:
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- `cat /sys/class/ec_su_axb35/fan2/rpm` to get current rpm of fan2
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- `echo fixed > /sys/class/ec_su_axb35/fan3/mode && echo 2 > /sys/class/ec_su_axb35/fan3/level` to switch fan3 to fixed mode and set speed to level 2
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- `echo balanced > /sys/class/ec_su_axb35/apu/power_mode` to set power mode to balanced (85W)
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You can also call `su_axb35_monitor` anywhere to monitor all available values in realtime:
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![su_axb35_monitor](./su_axb35_monitor.png)
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To apply specific settings at system startup, place them in your `rc.local` file or utilize any other methods for executing commands during boot, such as creating a systemd unit. In the future, these parameters will also be configurable through module options.
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#### Custom Curves
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The custom curves define temperature thresholds for fan power levels:
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- **Ramp-up curve** (`/sys/class/ec_su_axb35/fanX/rampup_curve`): temperature points where fan increases to the next level
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- **Ramp-down curve** (`/sys/class/ec_su_axb35/fanX/rampdown_curve`): temperature points where fan decreases to the previous level
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For example, with these settings:
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- `rampup_curve = 60,70,83,95,97`
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- `rampdown_curve = 40,50,80,94,96`
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**When CPU is heating up:**
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- Below 60°: Fan at level 0 (minimum)
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- At 60°: Increases to level 1
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- At 70°: Increases to level 2
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- At 83°: Increases to level 3
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- At 95°: Increases to level 4
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- At 97°: Increases to level 5 (maximum)
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**When CPU is cooling down:**
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- Above 96°: Fan stays at level 5
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- Below 96°: Decreases to level 4
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- Below 94°: Decreases to level 3
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- Below 80°: Decreases to level 2
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- Below 50°: Decreases to level 1
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- Below 40°: Decreases to level 0
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This creates a buffer at each level that prevents the fan from rapidly switching between speeds when temperature fluctuates around threshold values.
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Curves are being applied only when `curve` mode is set on a specific fan, each fan has their own curves.
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### Solution for Windows
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Based on the research made for the Linux module [a Windows implementation has been written as well](https://github.com/deseven/ec-su_axb35-win). The only major limitation is the need to disable Secure Boot, everything else should be pretty simple, just follow the readme in the repo.
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### Fine-tuning Power Limits
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If you want more gradual control over power modes, there's a [RyzenAdj](https://github.com/FlyGoat/RyzenAdj) utility (or [UXTU](https://amdaputuningutility.com) for Windows).
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Main 3 parameters we are interested in are:
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- `STAPM LIMIT` (sustained power draw)
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- `PPT LIMIT FAST` (boost power draw)
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- `PPT LIMIT SLOW` (average power draw)
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Default values on all 3 selectable power modes (use `ryzenadj --info` to read them):
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| Power Mode | STAPM LIMIT | PPT LIMIT FAST | PPT LIMIT SLOW |
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| ----------- | ----------- | -------------- | -------------- |
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| Quiet | 54.0 | 100.0 | 54.0 |
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| Balanced | 85.0 | 120.0 | 120.0 |
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| Performance | 120.0 | 140.0 | 120.0 |
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Example on setting the power limit to static 100W with no boost:
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`ryzenadj --stapm-limit=100000 --fast-limit=100000 --slow-limit=100000`
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**Note that changing the power mode via the EC controller (using `ec-su_axb35-linux` or otherwise) resets these values to their defaults.**
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### Relevant Pages
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- [[Guides/Hardware-Monitoring]]
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- [[Guides/Power-Modes-and-Performance]]