linux/Documentation/hwmon/pkgtemp
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   1Kernel driver pkgtemp
   2======================
   3
   4Supported chips:
   5  * Intel family
   6    Prefix: 'pkgtemp'
   7    CPUID:
   8    Datasheet: Intel 64 and IA-32 Architectures Software Developer's Manual
   9               Volume 3A: System Programming Guide
  10
  11Author: Fenghua Yu
  12
  13Description
  14-----------
  15
  16This driver permits reading package level temperature sensor embedded inside
  17Intel CPU package. The sensors can be in core, uncore, memory controller, or
  18other components in a package. The feature is first implemented in Intel Sandy
  19Bridge platform.
  20
  21Temperature is measured in degrees Celsius and measurement resolution is
  221 degree C. Valid temperatures are from 0 to TjMax degrees C, because the actual
  23value of temperature register is in fact a delta from TjMax.
  24
  25Temperature known as TjMax is the maximum junction temperature of package.
  26We get this from MSR_IA32_TEMPERATURE_TARGET. If the MSR is not accessible,
  27we define TjMax as 100 degrees Celsius. At this temperature, protection
  28mechanism will perform actions to forcibly cool down the package. Alarm
  29may be raised, if the temperature grows enough (more than TjMax) to trigger
  30the Out-Of-Spec bit. Following table summarizes the exported sysfs files:
  31
  32temp1_input       - Package temperature (in millidegrees Celsius).
  33temp1_max        - All cooling devices should be turned on.
  34temp1_crit        - Maximum junction temperature (in millidegrees Celsius).
  35temp1_crit_alarm - Set when Out-of-spec bit is set, never clears.
  36                    Correct CPU operation is no longer guaranteed.
  37