Note

This driver supersedes the NCT6775F and NCT6776F support in the W83627EHFdriver.

Description¶

This driver implements support for the Nuvoton NCT6775F, NCT6776F, and NCT6779Dand compatible super I/O chips.

The chips support up to 25 temperature monitoring sources. Up to 6 of those aredirect temperature sensor inputs, the others are special sources such as PECI,PCH, and SMBUS. Depending on the chip type, 2 to 6 of the temperature sourcescan be monitored and compared against minimum, maximum, and criticaltemperatures. The driver reports up to 10 of the temperatures to the user.There are 4 to 5 fan rotation speed sensors, 8 to 15 analog voltage sensors,one VID, alarms with beep warnings (control unimplemented), and some automaticfan regulation strategies (plus manual fan control mode).

The temperature sensor sources on all chips are configurable. The configuredsource for each of the temperature sensors is provided in tempX_label.

Temperatures are measured in degrees Celsius and measurement resolution iseither 1 degC or 0.5 degC, depending on the temperature source andconfiguration. An alarm is triggered when the temperature gets higher thanthe high limit; it stays on until the temperature falls below the hysteresisvalue. Alarms are only supported for temp1 to temp6, depending on the chip type.

Fan rotation speeds are reported in RPM (rotations per minute). An alarm istriggered if the rotation speed has dropped below a programmable limit. OnNCT6775F, fan readings can be divided by a programmable divider (1, 2, 4, 8,16, 32, 64 or 128) to give the readings more range or accuracy; the other chipsdo not have a fan speed divider. The driver sets the most suitable fan divisoritself; specifically, it increases the divider value each time a fan speedreading returns an invalid value, and it reduces it if the fan speed readingis lower than optimal. Some fans might not be present because they share pinswith other functions.

Voltage sensors (also known as IN sensors) report their values in millivolts.An alarm is triggered if the voltage has crossed a programmable minimumor maximum limit.

The driver supports automatic fan control mode known as Thermal Cruise.In this mode, the chip attempts to keep the measured temperature in apredefined temperature range. If the temperature goes out of range, fanis driven slower/faster to reach the predefined range again.

The mode works for fan1-fan5.

sysfs attributes¶

pwm[1-7]

• this file stores PWM duty cycle or DC value (fan speed) in range:

  0 (lowest speed) to 255 (full)

pwm[1-7]_enable

• this file controls mode of fan/temperature control:

  • 0 Fan control disabled (fans set to maximum speed)
  • 1 Manual mode, write to pwm[0-5] any value 0-255
  • 2 “Thermal Cruise” mode
  • 3 “Fan Speed Cruise” mode
  • 4 “Smart Fan III” mode (NCT6775F only)
  • 5 “Smart Fan IV” mode

pwm[1-7]_mode

• controls if output is PWM or DC level

  • 0 DC output
  • 1 PWM output

Common fan control attributes¶

pwm[1-7]_temp_sel

Temperature source. Value is temperature sensor index.For example, select ‘1’ for temp1_input.

pwm[1-7]_weight_temp_sel

Secondary temperature source. Value is temperaturesensor index. For example, select ‘1’ for temp1_input.Set to 0 to disable secondary temperature control.

If secondary temperature functionality is enabled, it is controlled with thefollowing attributes.

pwm[1-7]_weight_duty_step

Duty step size.

pwm[1-7]_weight_temp_step

Temperature step size. With each step overtemp_step_base, the value of weight_duty_step is addedto the current pwm value.

pwm[1-7]_weight_temp_step_base

Temperature at which secondary temperature control kicksin.

pwm[1-7]_weight_temp_step_tol

Temperature step tolerance.

Thermal Cruise mode (2)¶

If the temperature is in the range defined by:

pwm[1-7]_target_temp

Target temperature, unit millidegree Celsius(range 0 - 127000)

pwm[1-7]_temp_tolerance

Target temperature tolerance, unit millidegree Celsius

There are no changes to fan speed. Once the temperature leaves the interval, fanspeed increases (if temperature is higher that desired) or decreases (iftemperature is lower than desired), using the following limits and timeintervals.

pwm[1-7]_start

fan pwm start value (range 1 - 255), to start fanwhen the temperature is above defined range.

pwm[1-7]_floor

lowest fan pwm (range 0 - 255) if temperature is belowthe defined range. If set to 0, the fan is expected tostop if the temperature is below the defined range.

pwm[1-7]_step_up_time

milliseconds before fan speed is increased

pwm[1-7]_step_down_time

milliseconds before fan speed is decreased

pwm[1-7]_stop_time

how many milliseconds must elapse to switchcorresponding fan off (when the temperature was belowdefined range).

Speed Cruise mode (3)¶

This modes tries to keep the fan speed constant.

fan[1-7]_target

Target fan speed

fan[1-7]_tolerance

Target speed tolerance

Untested; use at your own risk.

Smart Fan IV mode (5)¶

This mode offers multiple slopes to control the fan speed. The slopes can becontrolled by setting the pwm and temperature attributes. When the temperaturerises, the chip will calculate the DC/PWM output based on the current slope.There are up to seven data points depending on the chip type. Subsequent datapoints should be set to higher temperatures and higher pwm values to achievehigher fan speeds with increasing temperature. The last data point reflectscritical temperature mode, in which the fans should run at full speed.

pwm[1-7]_auto_point[1-7]_pwm

pwm value to be set if temperature reaches matchingtemperature range.

pwm[1-7]_auto_point[1-7]_temp

Temperature over which the matching pwm is enabled.

pwm[1-7]_temp_tolerance

Temperature tolerance, unit millidegree Celsius

pwm[1-7]_crit_temp_tolerance

Temperature tolerance for critical temperature,unit millidegree Celsius

pwm[1-7]_step_up_time

milliseconds before fan speed is increased

pwm[1-7]_step_down_time

milliseconds before fan speed is decreased

Usage Notes¶

On various ASUS boards with NCT6776F, it appears that CPUTIN is not reallyconnected to anything and floats, or that it is connected to some non-standardtemperature measurement device. As a result, the temperature reported on CPUTINwill not reflect a usable value. It often reports unreasonably hightemperatures, and in some cases the reported temperature declines if the actualtemperature increases (similar to the raw PECI temperature value - see PECIspecification for details). CPUTIN should therefore be ignored on ASUSboards. The CPU temperature on ASUS boards is reported from PECI 0.