1.\" $NetBSD: odcm.4,v 1.6 2020/11/14 20:04:46 wiz Exp $ 2.\" 3.\" Copyright (c) 2011 Jukka Ruohonen <jruohonen@iki.fi> 4.\" All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Neither the name of the author nor the names of any 12.\" contributors may be used to endorse or promote products derived 13.\" from this software without specific prior written permission. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS 16.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 17.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 18.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 19.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 20.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 21.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 22.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 23.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 24.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 25.\" POSSIBILITY OF SUCH DAMAGE. 26.\" 27.Dd February 17, 2017 28.Dt ODCM 4 x86 29.Os 30.Sh NAME 31.Nm odcm 32.Nd On-demand Clock Modulation 33.Sh SYNOPSIS 34.Cd "odcm0 at cpu0" 35.Sh DESCRIPTION 36The 37.Nm 38driver provides support for changing the duty cycle of a 39.Tn CPU . 40This is sometimes known as 41.Dq on-demand clock modulation 42.Pq Tn ODCM . 43Refer to 44.Xr acpicpu 4 45for additional details about 46.Tn ODCM . 47.Pp 48The following 49.Xr sysctl 8 50variables are available with 51.Nm : 52.Bl -tag -width "machdep.clockmod.available " -offset indent 53.It Ic machdep.clockmod.target 54The target duty cycle of all 55.Tn CPUs . 56The values range from 7 (100 %) to 0 (approximately 13 %). 57.It Ic machdep.clockmod.current 58The current duty cycle of 59.Tn CPUs . 60.It Ic machdep.clockmod.available 61A list of available duty cycles. 62.El 63.Pp 64Note that some errata may limit the availability of some duty cycles. 65.Sh SEE ALSO 66.Xr acpicpu 4 , 67.Xr x86/est 4 , 68.Xr x86/powernow 4 69.Sh CAVEATS 70.Tn ODCM 71is meant for short-term thermal management, not power management. 72There is usually no reason for a system administrator 73to change the values manually. 74Lowering the duty cycle may dramatically decrease 75performance and responsiveness of the system. 76