1.\" $NetBSD: hpet.4,v 1.1 2010/08/06 16:42:31 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 August 6, 2010 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 acpi?" 35.Cd "hpet* at amdpcib?" 36.Cd "hpet* at ichlpcib?" 37.Sh DESCRIPTION 38The 39.Nm 40driver supports High Precision Event Timers 41.Pq Tn HPETs . 42The 43.Tn HPET 44architecture defines one main 64-bit counter and several 45additional timers with variable width. 46The minimum clock frequency of the main timecounter is 10 MHz, 47but much higher rates are common. 48The additional 32 or 64 -bit parts are typically accessible via 49.Tn MMIO 50that is set by the system 51.Tn BIOS 52through 53.Tn ACPI . 54.Pp 55As a 56.Tn HPET 57can provide higher interrupt rates than a 58.Tn RTC 59or 60.Xr attimer 4 , 61multimedia is one typical application context. 62The interrupt logic is configurable through 63.Tn I/O 64.Tn APIC , 65but a legacy mode is provided for older systems. 66.Sh SEE ALSO 67.Xr acpi 4 , 68.Xr attimer 4 , 69.Xr timecounter 9 70.Rs 71.%A Intel Corporation 72.%T IA-PC HPET (High Precision Event Timers) Specification 73.%N Revision 1.0a 74.%D October, 2004 75.%U http://www.intel.com/hardwaredesign/hpetspec_1.pdf 76.Re 77