77 lines
2.4 KiB
Groff
77 lines
2.4 KiB
Groff
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.\" $NetBSD: hpet.4,v 1.1 2010/08/06 16:42:31 jruoho Exp $
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.\"
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.\" Copyright (c) 2010 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 August 6, 2010
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.Dt HPET 4 x86
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.Os
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.Sh NAME
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.Nm hpet
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.Nd High Precision Event Timer
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.Sh SYNOPSIS
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.Cd "hpet* at acpi?"
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.Cd "hpet* at amdpcib?"
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.Cd "hpet* at ichlpcib?"
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.Sh DESCRIPTION
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The
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.Nm
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driver supports High Precision Event Timers
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.Pq Tn HPETs .
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The
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.Tn HPET
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architecture defines one main 64-bit counter and several
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additional timers with variable width.
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The minimum clock frequency of the main timecounter is 10 MHz,
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but much higher rates are common.
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The additional 32 or 64 -bit parts are typically accessible via
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.Tn MMIO
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that is set by the system
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.Tn BIOS
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through
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.Tn ACPI .
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.Pp
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As a
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.Tn HPET
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can provide higher interrupt rates than a
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.Tn RTC
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or
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.Xr attimer 4 ,
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multimedia is one typical application context.
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The interrupt logic is configurable through
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.Tn I/O
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.Tn APIC ,
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but a legacy mode is provided for older systems.
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.Sh SEE ALSO
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.Xr acpi 4 ,
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.Xr attimer 4 ,
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.Xr timecounter 9
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.Rs
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.%A Intel Corporation
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.%T IA-PC HPET (High Precision Event Timers) Specification
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.%N Revision 1.0a
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.%D October, 2004
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.%U http://www.intel.com/hardwaredesign/hpetspec_1.pdf
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.Re
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