.Dd February 17, 2014
.Dt CLOCKMOD 4
.Os
.Sh NAME
.Nm clockmod
.Nd device driver for Intel software controlled clock modulation
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device clockmod"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
clockmod_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides support for Intel software controlled clock modulation,
which reduces CPU core's duty cycle to reduce the power consumption.
A clock moduation domain contains logical CPUs on the same CPU core.
All logical CPUs in the same clock modulation domain will have the same
duty cycle setting.
.Sh MIB Variables
Clock modulation domain's information and controlling is provided by
.Va machdep.clockmod_dom Ns Em X
branch of the
.Xr sysctl 3
MIB.
.Bl -tag -width "available"
.It Va members
Logical CPUs belong to this clock modulation domain.
.It Va available
Available duty cycle settings for this clock modulation domain.
.It Va select
The current duty cycle setting for this clock modulation domain.
It could be set to any value listed in
.Va available .
The lower duty cycle the more power saving.
.El
.Sh SEE ALSO
.Xr sysctl 3 ,
.Xr sysctl 8