.\"	$OpenBSD: cpu.4,v 1.3 2007/10/31 16:25:22 jmc Exp $
.\"
.\" Copyright (c) 2004 Ted Unangst
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.Dd $Mdocdate: October 31 2007 $
.Dt CPU 4 amd64
.Os
.Sh NAME
.Nm cpu
.Nd Central Processing Unit
.Sh SYNOPSIS
.Cd "cpu0 at mainbus?"
.Cd "cpu* at mainbus?"
.Sh DESCRIPTION
Several processor models have additional features that extend their base
functionality, such as power and frequency control or thermal monitoring.
.Sh FREQUENCY CONTROL
The
.Xr sysctl 3
hw.cpuspeed will return the current operating frequency of the processor
(on some processors this value may be an approximation).
If possible, speed may be adjusted by altering hw.setperf from 0 to 100,
representing percentage of maximum speed.
There are several possible implementations for setperf, all transparent
to the user.
.Bl -tag -width tenletters
.It EST
Enhanced SpeedStep found on Intel processors,
offers frequency scaling with numerous positions.
.It PowerNow
Found on various AMD processors.
Currently only supports a limited set of models in the K8 families.
.El
.Sh THERMAL MONITORING
The
.Xr sysctl 3
hw.sensors.cpu*.temp0 will return the current temperature reported by the
processor.
.Sh SEE ALSO
.Xr sysctl 8
.Sh BUGS
Due to the way in which thermal information is reported on Intel processors,
the temperature may be off by exactly +/-15 degrees C.
.Pp
For multiprocessor kernels, processors will report identical temperatures
since the temperature is taken from the processor running the sensors update.