static/freebsd/man4/atrtc.4 4.html


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<table class="head">
  <tr>
    <td class="head-ltitle">ATRTC(4)</td>
    <td class="head-vol">Device Drivers Manual</td>
    <td class="head-rtitle">ATRTC(4)</td>
  </tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">atrtc</code> &#x2014; <span class="Nd">AT
    Real-Time Clock (RTC) driver</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp">This driver is a mandatory part of i386/amd64 kernels.</p>
<p class="Pp">The following tunables are settable from the
    <a class="Xr">loader(8)</a>:</p>
<dl class="Bl-ohang">
  <dt id="hint.atrtc."><var class="Va">hint.atrtc.</var><var class="Ar">X</var><var class="Va">.clock</var></dt>
  <dd>controls event timers functionality support. Setting to 0, disables it.
      Default value is 1.</dd>
  <dt id="hw.atrtc.enabled"><var class="Va">hw.atrtc.enabled</var></dt>
  <dd>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).</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">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.</p>
<p class="Pp">Event timer provided by the driver is irrelevant to CPU power
    states.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
  ALSO</a></h1>
<p class="Pp"><a class="Xr">apic(4)</a>, <a class="Xr">attimer(4)</a>,
    <a class="Xr">eventtimers(4)</a>, <a class="Xr">hpet(4)</a></p>
</section>
</div>
<table class="foot">
  <tr>
    <td class="foot-date">December 15, 2022</td>
    <td class="foot-os">FreeBSD 15.0</td>
  </tr>
</table>