Manual browser: adt7468(4)

DBCOOL(4) Kernel Interfaces Manual DBCOOL(4)


dbcool, adm1027, adm1030, adm1031, adt7463, adt7466, adt7467, adt7468, adt7473, adt7475, adt7476, adt7490, emc6d103sdbCool(tm) family of environmental monitors and fan controllers


dbcool* at ki2c?
dbcool* at iic? addr 0x2e


The dbcool driver provides support for the Analog Devices dbCool and the SMSC EMC6D103S environmental monitor chips to be used with the envsys(4) API.

These chips support up to fifteen sensors. Not all of the following sensors are supported on all chips.

Sensor Units Typical Use
l_temp uK local chip temperature
r1_temp uK CPU temperature
r2_temp uK GPU temperature
Vccp uV DC CPU Vcore
Vcc uV DC Chip's supply voltage
2.5V uV DC 2.5V supply
5V uV DC 5V supply
12V uV DC 12V supply
Vtt uV DC PECI ref. voltage (2.25V ref, ADT7490 only)
Imon uV DC Current monitor (2.25V ref, ADT7490 only)
AIN1 uV DC Analog In (2.25V ref, ADT7466 only)
AIN2 uV DC Analog In (2.25V ref, ADT7466 only)
fan1 RPM Chassis Fan
fan2 RPM Chassis Fan
fan3 RPM Chassis Fan
fan4 RPM Chassis Fan
VID (none) CPU VID code (selected chips only)

Each temperature and voltage sensor has programmable hardware high- and low-limits; fan sensors have only a low-limit. These limits can be set using the envstat(8) utility. Due to hardware limitations, the minimum permissible value for the fan speed low-limits is 83 RPM.

Temperature sensors also have Tmin, Trange, Thyst, and Ttherm sysctl(8) variables; these values are used by the fan speed controllers. Their values are in units of degC, since this is the unit which is programmed into the device registers.

All members of the dbCool family support Pulse-Width Modulated (PWM) fan speed control based on temperature thresholds - the fan will spin up when its associated thermal sensor(s) exceeds its configured Tmin value. The fan will go faster as the temperature rises, and will slow down as the temperature falls. If the temperature exceeds the sensor's Ttherm value, the THERM signal will be asserted, and if enabled the fan will run at full speed. The fan will be turned off when the sensor(s) that triggered it reports a temperature which is at least Thyst degrees below its Tmin threshold.

Each fan controller is programmable using the following sysctl(8) variables.


The behavior variable controls the selection of temperature sensors associated with the fan controller. When the associated temperature sensor reaches its Tmin value, the fan controller starts the fan at its minimum duty cycle; when the associated temperature sensor reaches its Ttherm value and asserts the THERM signal (or if an external THERM signal is asserted), the fan controller sets the fan speed to a 100% duty cycle. Between these two settings, each temperature sensor is used to calculate a duty cycle linearly based on the slope defined by the temperature sensor's range variable. When the associated temperature falls at least Thyst degress below its Tmin value, the fan controller will turn off the fan. (On the ADM1030, the value for Thyst is fixed at 5 degC.)

Valid values for the behavior variable are:

local           (not available on ADM1030) 
remote2         (not available on ADM1030) 
local+remote2   (not available on ADM1030) 
full-speed      (not available on ADM1030) 

When the behavior variable is set to “manual”, the cur-duty variable becomes user-writable and can be set to any value between 0 and 100 inclusive to control the fan's duty cycle manually. In all other behavior modes, the cur-duty variable is read-only and updates are ignored.

The min-duty and max-duty variables define the range over which the fan controller will manage the fan's duty cycle. On the ADM1030, these values are not separately controllable. The max-duty is fixed at 100%, and the cur-duty variable is used to specify the minimum duty cycle when the fan controller is running in automatic mode.

Note that the duty-cycle value does not directly correspond to the fan's speed. That is, a 33% duty cycle does not mean that the fan runs at 33% of its maximum speed; in actuality, a 33% duty cycle drives the fan at a speed close to 50% of its maximum. Fan speed correlates approximately to the square root of the duty cycle.


The envstat(8) utility can be used to determine the sensors supported:

            Current  CritMax  WarnMax  WarnMin  CritMin Unit 
 l_temp:     44.250                                     degC 
r1_temp:     41.250                                     degC 
r2_temp:        N/A 
   Vccp:      0.002                                     V 
    Vcc:      3.351                                     V 
   fan1:        N/A 
   fan2:        N/A 
   fan3:        N/A 
   fan4:        N/A

Using this information, the following commands in /etc/envsys.conf will set appropriate limits for CPU temperature and chip supply voltage, and powerd will be notified if the limits are exceeded:

dbcool0 { 
        sensor1 { 
                warning-max  = 60C; 
                critical-max = 65C; 
        sensor4 { 
                critical-min = 3.1; 
                warning-min =  3.2; 
                critical-max = 3.5; 


The dbcool device appeared in NetBSD 5.0.


Although the sensor limit registers can be programmed, there is currently no use of the dbCool chips' ability to generate an SMBus interrupt when the limits are exceeded. Limit checking and event generation are done in software, and are performed only when the sensor values are polled and refreshed.

The ADT7466 chip, although officially a member of the dbCool family, is programmed quite differently. The fan controllers on this chip are not currently implemented.

The PECI (Processor Environment Control Interface) temperature sensors and the associated PWM behavior modes on the ADT7490 are not currently supported.

March 12, 2011 NetBSD 7.0