Documentation/hwmon/nct6775

   1 Note
   2 ====
   3
   4 This driver supersedes the NCT6775F and NCT6776F support in the W83627EHF
   5 driver.
   6
   7 Kernel driver NCT6775
   8 =====================
   9
  10 Supported chips:
  11   * Nuvoton NCT6775F/W83667HG-I
  12     Prefix: 'nct6775'
  13     Addresses scanned: ISA address retrieved from Super I/O registers
  14     Datasheet: Available from Nuvoton upon request
  15   * Nuvoton NCT6776F
  16     Prefix: 'nct6776'
  17     Addresses scanned: ISA address retrieved from Super I/O registers
  18     Datasheet: Available from Nuvoton upon request
  19   * Nuvoton NCT6779D
  20     Prefix: 'nct6779'
  21     Addresses scanned: ISA address retrieved from Super I/O registers
  22     Datasheet: Available from Nuvoton upon request
  23
  24 Authors:
  25         Guenter Roeck <linux@roeck-us.net>
  26
  27 Description
  28 -----------
  29
  30 This driver implements support for the Nuvoton NCT6775F, NCT6776F, and NCT6779D
  31 super I/O chips.
  32
  33 The chips support up to 25 temperature monitoring sources. Up to 6 of those are
  34 direct temperature sensor inputs, the others are special sources such as PECI,
  35 PCH, and SMBUS. Depending on the chip type, 2 to 6 of the temperature sources
  36 can be monitored and compared against minimum, maximum, and critical
  37 temperatures. The driver reports up to 10 of the temperatures to the user.
  38 There are 4 to 5 fan rotation speed sensors, 8 to 15 analog voltage sensors,
  39 one VID, alarms with beep warnings (control unimplemented), and some automatic
  40 fan regulation strategies (plus manual fan control mode).
  41
  42 The temperature sensor sources on all chips are configurable. The configured
  43 source for each of the temperature sensors is provided in tempX_label.
  44
  45 Temperatures are measured in degrees Celsius and measurement resolution is
  46 either 1 degC or 0.5 degC, depending on the temperature source and
  47 configuration. An alarm is triggered when the temperature gets higher than
  48 the high limit; it stays on until the temperature falls below the hysteresis
  49 value. Alarms are only supported for temp1 to temp6, depending on the chip type.
  50
  51 Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
  52 triggered if the rotation speed has dropped below a programmable limit. On
  53 NCT6775F, fan readings can be divided by a programmable divider (1, 2, 4, 8,
  54 16, 32, 64 or 128) to give the readings more range or accuracy; the other chips
  55 do not have a fan speed divider. The driver sets the most suitable fan divisor
  56 itself; specifically, it increases the divider value each time a fan speed
  57 reading returns an invalid value, and it reduces it if the fan speed reading
  58 is lower than optimal. Some fans might not be present because they share pins
  59 with other functions.
  60
  61 Voltage sensors (also known as IN sensors) report their values in millivolts.
  62 An alarm is triggered if the voltage has crossed a programmable minimum
  63 or maximum limit.
  64
  65 The driver supports automatic fan control mode known as Thermal Cruise.
  66 In this mode, the chip attempts to keep the measured temperature in a
  67 predefined temperature range. If the temperature goes out of range, fan
  68 is driven slower/faster to reach the predefined range again.
  69
  70 The mode works for fan1-fan5.
  71
  72 Usage Notes
  73 -----------
  74
  75 On various ASUS boards with NCT6776F, it appears that CPUTIN is not really
  76 connected to anything and floats, or that it is connected to some non-standard
  77 temperature measurement device. As a result, the temperature reported on CPUTIN
  78 will not reflect a usable value. It often reports unreasonably high
  79 temperatures, and in some cases the reported temperature declines if the actual
  80 temperature increases (similar to the raw PECI temperature value - see PECI
  81 specification for details). CPUTIN should therefore be be ignored on ASUS
  82 boards. The CPU temperature on ASUS boards is reported from PECI 0.