76 lines
2.5 KiB
Groff
76 lines
2.5 KiB
Groff
.\" $NetBSD: odcm.4,v 1.4 2011/03/04 13:49:26 wiz Exp $
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.\"
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.\" Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Neither the name of the author nor the names of any
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd March 4, 2011
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.Dt ODCM 4
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.Os
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.Sh NAME
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.Nm odcm
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.Nd On-demand Clock Modulation
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.Sh SYNOPSIS
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.Cd "odcm0 at cpu0"
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.Sh DESCRIPTION
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The
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.Nm
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driver provides support for changing the duty cycle of a
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.Tn CPU .
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This is sometimes known as
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.Dq on-demand clock modulation
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.Pq Tn ODCM .
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Refer to
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.Xr acpicpu 4
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for additional details about
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.Tn ODCM .
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.Pp
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The following
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.Xr sysctl 8
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variables are available with
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.Nm :
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.Bl -tag -width "machdep.clockmod.available " -offset indent
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.It Ic machdep.clockmod.target
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The target duty cycle of all
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.Tn CPUs .
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The values range from 7 (100 %) to 0 (approximately 13 %).
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.It Ic machdep.clockmod.current
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The current duty cycle of
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.Tn CPUs .
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.It Ic machdep.clockmod.available
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A list of available duty cycles.
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.El
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.Pp
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Note that some errata may limit the availability of some duty cycles.
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.Sh SEE ALSO
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.Xr acpicpu 4 ,
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.Xr est 4 ,
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.Xr powernow 4
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.Sh CAVEATS
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.Tn ODCM
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is meant for short-term thermal management, not power management.
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There is usually no reason for a system administrator
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to change the values manually.
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Lowering the duty cycle may dramatically decrease
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performance and responsiveness of the system.
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