59 lines
2.3 KiB
Groff
59 lines
2.3 KiB
Groff
.\" Copyright (c) 2010 Alexander Motin <mav@FreeBSD.org>
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd September 17, 2010
|
|
.Dt ATRTC 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm atrtc
|
|
.Nd AT Real-Time Clock (RTC) driver
|
|
.Sh SYNOPSIS
|
|
This driver is a mandatory part of i386/amd64 kernels.
|
|
.Pp
|
|
The following tunable is settable from the
|
|
.Xr loader 8 :
|
|
.Bl -ohang
|
|
.It Va hint.atrtc. Ns Ar X Ns Va .clock
|
|
controls event timers functionality support.
|
|
Setting to 0, disables it.
|
|
Default value is 1.
|
|
.El
|
|
.Sh DESCRIPTION
|
|
This driver uses RTC hardware to supply kernel with time-of-day clock
|
|
with 1 second resolution and one event timer.
|
|
This hardware uses base frequency of 32768Hz for advancing time-of-day clock
|
|
and generating periodic interrupts.
|
|
Interrupts could be generated with fixed number of frequencies, from 2Hz to
|
|
8192Hz, obtained by dividing base frequency by one of supported power-of-2
|
|
divisors.
|
|
.Pp
|
|
Event timer provided by the driver is irrelevant to CPU power states.
|
|
.Sh SEE ALSO
|
|
.Xr apic 4 ,
|
|
.Xr attimer 4 ,
|
|
.Xr eventtimers 4 ,
|
|
.Xr hpet 4
|