CPU Fan Control

Modern Intel and AMD processors report several readings: individual core temperatures, a package or die temperature, and on AMD the Tctl/Tdie values. For fan control, the package temperature is the most useful because it tracks the hottest part of the chip without the extreme jitter of a single core. Fan Control lists all of them as temperature sources; choose the package reading and, if the fan still hunts, wrap it in a Time Average custom sensor that smooths over a few seconds.

The CPU cooler plugs into the header labeled CPU_FAN, with a second CPU_OPT or AIO_PUMP header nearby. Each header is driven by the motherboard’s Super I/O chip, which is what Fan Control talks to through LibreHardwareMonitor. Headers can run in PWM mode, where a 25 kHz signal tells a four-pin fan how fast to spin, or DC mode, where the header changes voltage for a three-pin fan. Set the mode to match the fan in the BIOS first; software cannot fix a header left in the wrong mode. More on that in the PWM fan control guide.

Every board ships with a firmware fan profile, and it has one big advantage: it works before Windows starts and keeps working if the operating system freezes. Its weakness is that it only sees the sensors the board knows about and offers a handful of fixed points. Fan Control runs on top of it. Keep a conservative profile in the BIOS as a safety net, then let the app apply a smarter curve once you sign in. If the app is closed or crashes, the firmware profile takes over again within seconds.

1. Pair the CPU fan control with its RPM sensor and run calibration so the app knows the fan’s start and stop points.
2. Create a Linear curve using the package temperature: roughly 30% at 40 °C rising to 100% at the processor’s rated maximum minus a margin, for example 85 °C on a chip rated for 95 °C.
3. Add 2 to 3 °C of hysteresis and a response time of a couple of seconds so boost spikes do not trigger a ramp.
4. Set a minimum percentage instead of allowing the CPU fan to stop entirely; a slowly spinning cooler is nearly silent and keeps the VRM area ventilated.
5. Stress the system for ten minutes and check that temperatures level off well below the limit. If not, steepen the upper part of the curve.

Never rely on a curve that lets the processor sit at its thermal limit. Modern CPUs throttle to protect themselves, but sustained throttling costs performance and a curve that leaves margin is always the better trade.

Tower air coolers respond quickly to fan changes. All-in-one liquid coolers behave differently: the coolant warms slowly, so radiator fans should follow the liquid temperature when the AIO exposes it, or a heavily averaged CPU temperature when it does not. Keep the pump at a fixed high speed with a Flat curve; varying pump speed adds noise and little cooling benefit. Popular AIOs from Corsair, NZXT and others are supported directly or through community plugins.

If the CPU_FAN header does not appear as a control, check that no vendor utility is running, that the app was started with administrator rights, and that your motherboard chip is supported. Some boards expose the CPU header as read-only when Smart Fan mode is enabled in the BIOS; switching the header to manual or full-speed mode in firmware usually unlocks it for software. The Windows 11 guide has a longer checklist.

• GPU fan control
• How to control PC fan speed in Windows
• Download Fan Control