ATRTC(4)               FreeBSD 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.
     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 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 13.1-RELEASE-p6       September 17, 2010       FreeBSD 13.1-RELEASE-p6