SMNTEMP(4D) Devices SMNTEMP(4D)

NAME

smntemp - AMD SMN Temperature Sensor Driver

SYNOPSIS

/dev/sensors/temperature/cpu/*

DESCRIPTION

The smntemp driver provides the system access to the temperature and
control sensors found in the AMD System Management Network (SMN) on Zen 1-5
processors (AMD Family 17h, 19h, and 1ah).

Each CCD, core complex die, present in the SoC exposes its own temperature
in degrees Celsius. This covers the temperature of the CCD as a whole and
could be thought of as a temperature sensor for all the cores and caches in
the die. There is no per-core temperature sensor available.

In addition, a control temperature is exposed for each I/O die, Zen 2 and
newer, or each Zeppelin die, Zen 1. The control temperature is a unitless
measure derived from the temperature that indicates to cooling
infrastructure what action to take and can take any value on the range 0 to
100. A value of 95 indicates that thermal throttling should be occurring
and a value of 100 indicates that the chip will hit its thermal limit and
shut down if no action is taken. Critically, the control temperature is
not truly a measure of degrees!

Temperature information is available to the system via the fault management
architecture (FMA). The file system location and programming interface to
the smntemp driver are considered Volatile, subject to change without
notice, and should not be used directly. Raw temperature information can
be dumped through the FMA developer utility fmtopo.

SEE ALSO

amdnbtemp(4D), amdzen(4D), fmadm(8)

AMD, Open-Source Register Reference For AMD Family 17h Processors Models
00h-2Fh, July, 2018.

illumos May 22, 2024 illumos