Kernel driver nct7904

Supported chip:

  • Nuvoton NCT7904D

    Prefix: nct7904

    Addresses: I2C 0x2d, 0x2e

    Datasheet: Publicly available at Nuvoton website

Author: Vadim V. Vlasov <>


The NCT7904D is a hardware monitor supporting up to 20 voltage sensors, internal temperature sensor, Intel PECI and AMD SB-TSI CPU temperature interface, up to 12 fan tachometer inputs, up to 4 fan control channels with SmartFan.

Sysfs entries

Currently, the driver supports only the following features:

in[1-20]_input Input voltage measurements (mV)
fan[1-12]_input Fan tachometer measurements (rpm)
temp1_input Local temperature (1/1000 degree, 0.125 degree resolution)
temp[2-9]_input CPU temperatures (1/1000 degree, 0.125 degree resolution)
pwm[1-4]_enable R/W, 1/2 for manual or SmartFan mode Setting SmartFan mode is supported only if it has been previously configured by BIOS (or configuration EEPROM)
pwm[1-4] R/O in SmartFan mode, R/W in manual control mode

The driver checks sensor control registers and does not export the sensors that are not enabled. Anyway, a sensor that is enabled may actually be not connected and thus provide zero readings.


The following features are not supported in current version:

  • SmartFan control
  • Watchdog
  • GPIO
  • external temperature sensors
  • SMI
  • min/max values
  • many other…