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.\" Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
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.Dd February 17, 2017
.Dt ODCM 4
.Os
.Sh NAME
.Nm odcm
.Nd On-demand Clock Modulation
.Sh SYNOPSIS
.Cd "odcm0 at cpu0"
.Sh DESCRIPTION
The
.Nm
driver provides support for changing the duty cycle of a
.Tn CPU .
This is sometimes known as
.Dq on-demand clock modulation
.Pq Tn ODCM .
Refer to
.Xr acpicpu 4
for additional details about
.Tn ODCM .
.Pp
The following
.Xr sysctl 8
variables are available with
.Nm :
.Bl -tag -width "machdep.clockmod.available " -offset indent
.It Ic machdep.clockmod.target
The target duty cycle of all
.Tn CPUs .
The values range from 7 (100 %) to 0 (approximately 13 %).
.It Ic machdep.clockmod.current
The current duty cycle of
.Tn CPUs .
.It Ic machdep.clockmod.available
A list of available duty cycles.
.El
.Pp
Note that some errata may limit the availability of some duty cycles.
.Sh SEE ALSO
.Xr acpicpu 4 ,
.Xr x86/est 4 ,
.Xr x86/powernow 4
.Sh CAVEATS
.Tn ODCM
is meant for short-term thermal management, not power management.
There is usually no reason for a system administrator
to change the values manually.
Lowering the duty cycle may dramatically decrease
performance and responsiveness of the system.