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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	periodic  inter-
     rupts.   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 15.1			December 15, 2022			ATRTC(4)

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