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ATRTC(4)		    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.enabled
       Forces enabling or disabling of the device(s).  Setting to  0  disables
       it,  setting  to	 1  enables  it,  bypassing any	platform configuration
       hints.  Default 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 pe-
       riodic 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.

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

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

FreeBSD	14.3		       December	15, 2022		      ATRTC(4)

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