CAGT

AMD Fan Control
hwmon • PWM • Fan curves • Daemon

Small enough to read in one sitting.
Complete enough to actually cool your GPU.

What it is • Features • Quick start • Daemon • Fan curves • Safety model • Requirements • Supported GPUs

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What it is

CAGT is a fan controller for AMD GPUs on Linux. It reads the GPU temperature from hwmon, runs it through a fan curve, and writes the resulting PWM value back. It runs either as a ncurses TUI or as a background daemon with a CLI.

Features

• ncurses TUI with color-coded temperatures and fan curve preview
• Background daemon with a Unix socket CLI
• Multi-GPU: tabbed title bar, per-GPU independent state
• Three control modes: curve, manual, hardware
• Five fan curves: Default, Quiet, Aggressive, Linear, Custom
• Custom curves via ~/.config/cagt/custom_curve.conf
• Multi-sensor: Edge, Junction, Memory where exposed by the driver
• Manual override with 1% and 5% steps, plus instant presets
• Temperature units: Celsius, Fahrenheit, Kelvin
• Peak temperature tracking with reset
• Zero RPM detection
• Runtime counter
• Optional CSV logging
• Persistent per-GPU settings in ~/.config/cagt/config.conf
• RDNA3+ fan_curve interface support via gpu_od/fan_ctrl/fan_curve
• ppfeaturemask detection with RDNA3+ warnings
• Safe exit with verified auto-restore, including pwm1_enable retry
• GPU detection table covering Polaris, Vega, Navi, RDNA3, RDNA4, and older GCN

Quick start

Build

gcc -std=c99 -O2 -o cagt cagt.c -lncurses
chmod +x cagt

For development:

gcc -std=c99 -O2 -Wall -Wextra -Wpedantic -Wno-format-truncation -o cagt cagt.c -lncurses

The production build does not need these flags.

Run

sudo ./cagt

Or as a daemon:

sudo ./cagt --daemon
./cagt status
./cagt fan 75
./cagt quit

Root is required. CAGT writes to /sys/class/drm/.../hwmon/.../pwm1 and reads the corresponding temperature and RPM files.

TUI controls

Key	Action
1 – 9	Select GPU (multi-GPU systems)
M	Cycle mode (curve / manual / hardware)
T	Cycle temperature unit (°C → °F → K)
S	Cycle temp sensor (Edge / Junction / Memory)
C	Cycle fan curve
R	Reset peak temperature
+ / -	Adjust fan by ±5% (enters manual)
↑ / ↓	Adjust fan by ±1% (enters manual)
0	Set fan to 0% instantly
Q	Quit (restores auto fan control)

Manual adjustments auto-switch into manual mode.

Daemon

cagt --daemon forks to the background and listens on a Unix socket. The CLI talks to that socket. If the daemon is not running and you issue a command, it tells you to start it. If the daemon is running and you launch cagt with no arguments, it tells you so.

Socket path: $XDG_RUNTIME_DIR/cagt.sock if set, otherwise /tmp/cagt-$UID/sock in a 0755 directory.

Command	Action
cagt status	Show temperature, fan speed, RPM, mode
cagt gpu <1-N>	Select active GPU
cagt fan <0-100>	Set manual fan speed
cagt fan auto	CAGT controls the fan via curve
cagt fan gpu	GPU hardware controls the fan
cagt curve <name|0-4>	Select curve
cagt curve list	List available curves
cagt log <interval>	Set logging interval (1s, 5s, 10s, 500ms, off)
cagt quit	Stop the daemon

Fan curves

Curves map temperature to fan speed. Between points, values are linearly interpolated. Five curves ship with CAGT.

Default

Temp (°C)	Fan Speed
20	0%
35	20%
50	30%
60	45%
70	60%
80	75%
90	90%
100	100%

Also available: Quiet, Aggressive, Linear.

Custom

Create ~/.config/cagt/custom_curve.conf:

# Format: temperature_c fan_percent
20 0
40 20
55 35
65 50
75 70
85 90
100 100

At least two points. Temperatures must be ascending. Select with cagt curve custom or cycle to it in the TUI with C.

On RDNA3+, CAGT writes curve points directly to gpu_od/fan_ctrl/fan_curve and lets the hardware interpolate. On older GPUs, CAGT recomputes the curve each tick and writes PWM.

Safety model

CAGT writes to /sys. If it dies without restoring auto mode, the GPU firmware is left wherever the last PWM write put it. Every exit path is designed around that.

Layer	Mechanism	Verified by
CAGT → pwm1	Write on tick, only on change	read-back optional
CAGT → pwm1_enable on start	Set to 1 (manual)	checked after write
CAGT → pwm1_enable on exit	Set to 2 (auto)	re-read and verified, retried on failure
RDNA3+ exit	fan_curve reset to r, then pwm1_enable=2	read-back on pwm1_enable
Crash handler	SIGINT, SIGTERM set flag, loop restores	async-signal-safe
Daemon → client	Unix socket	SO_PEERCRED uid check
custom_curve.conf	Parsed at load	rejected if fewer than 2 points or non-ascending temps
config.conf	Parsed at load	per-GPU state, unknown keys ignored

Zero RPM is detected and treated as valid. CAGT does not force the fan on below the curve's first non-zero point.

Not covered: CAGT does not stop the amdgpu driver from overriding pwm1_enable if ppfeaturemask is not set on RDNA3+. It warns on startup. It does not stop you from setting 0% manually and walking away. It does not persist across reboots — the daemon has to be started again.

Requirements

Always:

• gcc or clang
• ncurses development headers
• Linux with hwmon fan control exposed by amdgpu

By feature:

Feature	Extra
Manual fan on RDNA3+	amdgpu.ppfeaturemask=0xffffffff in kernel cmdline
Custom curve	~/.config/cagt/custom_curve.conf
Daemon mode	nothing extra
CSV logging	--log flag

Install ncurses:

# Artix / Arch
sudo pacman -S ncurses

# Debian / Ubuntu
sudo apt install libncurses-dev

# Fedora
sudo dnf install ncurses-devel

# Void
sudo xbps-install ncurses-devel

RDNA3+ note

RX 7000 and RX 9000 series GPUs require the amdgpu overdrive bit for manual fan control. Add this to your kernel cmdline or /etc/modprobe.d/amdgpu.conf:

amdgpu.ppfeaturemask=0xffffffff

Reboot. If CAGT prints a ppfeaturemask warning on startup, this is why.

Supported GPUs

Generation	Models
Polaris	RX 560, RX 570, RX 580 (incl. 2048SP)
Vega	RX Vega 56, Vega 64, Radeon VII
Navi 10	RX 5500 XT, RX 5600 XT, RX 5700, RX 5700 XT
Navi 20	RX 6300, RX 6400, RX 6500 XT, RX 6600, RX 6600 XT, RX 6650 XT, RX 6700, RX 6700 XT, RX 6800, RX 6800 XT, RX 6900 XT, RX 6950 XT
Navi 30 (RDNA3)	RX 7600, RX 7700 XT, RX 7800 XT, RX 7900 XT, RX 7900 XTX
Navi 40 (RDNA4)	RX 9060 XT, RX 9070, RX 9070 XT
Older GCN	HD 7950, HD 7970, R9 290/390, R9 Fury

Unknown AMD GPUs with a hwmon fan interface still work. They show their PCI device ID instead of a name.

Project structure

CAGT/
├── cagt.c           # the entire program
├── LICENSE          # IRX License 1.0
├── CONTRIBUTING     # contribution guidelines
└── README.md        # this file

Contributing

Contributions welcome. CAGT is intentionally a single file with no dependencies beyond ncurses. Keep it that way.

See CONTRIBUTING for guidelines.

License

CLEAR v1 license. See LICENSE.