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ATRTC(4)		 BSD Kernel Interfaces Manual		      ATRTC(4)

NAME
     atrtc -- AT Real-Time Clock (RTC) driver

SYNOPSIS
     This driver is a mandatory	part of	i386/amd64 kernels.

     The following tunables are	settable from the loader(8):

     hint.atrtc.X.clock
     controls event timers functionality support.  Setting to 0, disables it.
     Default value is 1.

     hw.atrtc.enable
     Forces enabling or	disabling of the device(s).  Setting to	0 disables it,
     setting to	1 enables it, bypassing	any platform configuration hints.  De-
     fault value is -1 (autodetect).

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 peri-
     odic interrupts.  Interrupts could	be generated with fixed	number of fre-
     quencies, from 2Hz	to 8192Hz, obtained by dividing	base frequency by one
     of	supported power-of-2 divisors.

     Event timer provided by the driver	is irrelevant to CPU power states.

SEE ALSO
     apic(4), attimer(4), eventtimers(4), hpet(4)

BSD			      September	17, 2010			   BSD

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO

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