1.\" $NetBSD: hpet.4,v 1.3 2011/06/14 13:59:24 jruoho Exp $ 2.\" 3.\" Copyright (c) 2010 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 June 14, 2011 28.Dt HPET 4 x86 29.Os 30.Sh NAME 31.Nm hpet 32.Nd High Precision Event Timer 33.Sh SYNOPSIS 34.Cd "hpet* at acpihpetbus?" 35.Cd "hpet* at acpinodebus?" 36.Cd "hpet* at amdpcib?" 37.Cd "hpet* at ichlpcib?" 38.Sh DESCRIPTION 39The 40.Nm 41driver supports High Precision Event Timers 42.Pq Tn HPETs . 43The 44.Tn HPET 45architecture defines one main 64-bit counter and several 46additional timers with variable width. 47The minimum clock frequency of the main timecounter is 10 MHz, 48but much higher rates are common. 49The additional 32 or 64 -bit parts are typically accessible via 50.Tn MMIO 51that is set by the system 52.Tn BIOS 53through 54.Tn ACPI . 55.Pp 56As a 57.Tn HPET 58can provide higher interrupt rates than a 59.Tn RTC 60or 61.Xr attimer 4 , 62multimedia is one typical application context. 63The interrupt logic is configurable through 64.Tn I/O 65.Tn APIC , 66but a legacy mode is provided for older systems. 67.Sh SEE ALSO 68.Xr acpi 4 , 69.Xr attimer 4 , 70.Xr timecounter 9 , 71.Xr tsc 9 72.Rs 73.%A Intel Corporation 74.%T IA-PC HPET (High Precision Event Timers) Specification 75.%N Revision 1.0a 76.%D October, 2004 77.%U http://www.intel.com/hardwaredesign/hpetspec_1.pdf 78.Re 79