.\"	$OpenBSD: dfs.4,v 1.2 2011/05/25 18:13:54 jmc Exp $
.\"
.\" Copyright (c) 2011 Martin Pieuchot <mpi@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: May 25 2011 $
.Dt DFS 4 macppc
.Os
.Sh NAME
.Nm dfs
.Nd Dynamic Frequency Switching
.Sh SYNOPSIS
.Cd "dfs* at macgpio?"
.Sh DESCRIPTION
The
.Nm
driver provides support for the Dynamic Frequency Switching
feature found on some PowerPC microprocessors.
.Pp
It conserves power by lowering the processor operating frequency.
Depending on the processor model, the processor-to-system bus ratio can
be divided by two or four.
.Sh HARDWARE
Processors supported by the
.Nm
driver are part of the PowerPC G4 family and are found on various iBook
and PowerBook machines:
.Bd -literal -offset indent
MPC7447A	PowerPC 7447 "Apollo 7"
MPC7448		PowerPC 7448 "Apollo 8"
.Ed
.Sh SEE ALSO
.Xr macgpio 4 ,
.Xr sysctl 8
.Rs
.%T MPC7450 RISC Microprocessor Family Reference Manual
.Re
.Sh HISTORY
Support for the
.Nm
driver first appeared in
.Ox 5.0 .