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.\" Copyright 2019, Joyent, Inc.
.\" Copyright 2024 Oxide Computer Company
.\"
.Dd May 22, 2024
.Dt SMNTEMP 4D
.Os
.Sh NAME
.Nm smntemp
.Nd AMD SMN Temperature Sensor Driver
.Sh SYNOPSIS
.Pa /dev/sensors/temperature/cpu/*
.Sh DESCRIPTION
The
.Nm
driver provides the system access to the temperature and control sensors found
in the AMD System Management Network
.Pq SMN
on Zen 1-5 processors
.Pq AMD Family 17h, 19h, and 1ah .
.Pp
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.
.Pp
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!
.Pp
Temperature information is available to the system via the fault
management architecture
.Pq FMA .
The file system location and programming interface to the
.Nm
driver are considered
.Sy Volatile ,
subject to change without notice, and should not be used directly.
Raw temperature information can be dumped through the FMA developer
utility fmtopo.
.Sh SEE ALSO
.Xr amdnbtemp 4D ,
.Xr amdzen 4D ,
.Xr fmadm 8
.Rs
.%A AMD
.%B Open-Source Register Reference For AMD Family 17h Processors Models 00h-2Fh
.%D July, 2018
.Re