+
+
+Fan Control
+-----------
+
+Both PWM (pulse-width modulation) and DC fan speed control methods are
+supported. The right one to use depends on external circuitry on the
+motherboard, so the driver assumes that the BIOS set the method
+properly. The driver will report the method, but won't let you change
+it.
+
+When the PWM method is used, you can select the operating frequency,
+from 187.5 kHz (default) to 31 Hz. The best frequency depends on the
+fan model. As a rule of thumb, lower frequencies seem to give better
+control, but may generate annoying high-pitch noise. Fintek recommends
+not going below 1 kHz, as the fan tachometers get confused by lower
+frequencies as well.
+
+When the DC method is used, Fintek recommends not going below 5 V, which
+corresponds to a pwm value of 106 for the driver. The driver doesn't
+enforce this limit though.
+
+Three different fan control modes are supported:
+
+* Manual mode
+ You ask for a specific PWM duty cycle or DC voltage.
+
+* Fan speed mode
+ You ask for a specific fan speed. This mode assumes that pwm1
+ corresponds to fan1, pwm2 to fan2 and pwm3 to fan3.
+
+* Temperature mode
+ You define 3 temperature/fan speed trip points, and the fan speed is
+ adjusted depending on the measured temperature, using interpolation.
+ This mode is not yet supported by the driver.