static/freebsd/man4/ichwd.4 3.html


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<table class="head">
  <tr>
    <td class="head-ltitle">ICHWD(4)</td>
    <td class="head-vol">Device Drivers Manual</td>
    <td class="head-rtitle">ICHWD(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">ichwd</code> &#x2014; <span class="Nd">device
    driver for the Intel ICH watchdog interrupt timer</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp">To compile this driver into the kernel, place the following line
    in your kernel configuration file:</p>
<div class="Bd Pp Bd-indent"><code class="Cd">device ichwd</code></div>
<p class="Pp">Alternatively, to load the driver as a module at boot time, place
    the following line in <a class="Xr">loader.conf(5)</a>:</p>
<div class="Bd Pp Bd-indent Li">
<pre>ichwd_load=&quot;YES&quot;</pre>
</div>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The <code class="Nm">ichwd</code> driver provides
    <a class="Xr">watchdog(4)</a> support for the watchdog interrupt timer
    present on all Intel ICH motherboard chipsets.</p>
<p class="Pp">The ICH WDT counts down in ticks of approximately 0.6 seconds; the
    exact value depends on hardware quality and environmental factors. Supported
    watchdog intervals range from 2 to 63 ticks.</p>
<p class="Pp">In QEMU, there is a dedicated watchdog implementation for x86
    systems based on the Intel 6300ESB controller hub. Support for this watchdog
    is provided by this kernel module.</p>
<p class="Pp">Optionally, set the <var class="Va">hw.i6300esbwd.x.locked=1</var>
    <a class="Xr">sysctl(8)</a> to prevent users from disabling the watchdog
    timeout check after it has been enabled.</p>
<p class="Pp">Note that on some ICH-based systems, the WDT may be present but
    disabled, either in hardware or by the BIOS. The
    <code class="Nm">ichwd</code> driver attempts to detect this condition and
    will refuse to attach if it believes the WDT is disabled.</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">watchdog(4)</a>, <a class="Xr">watchdog(8)</a>,
    <a class="Xr">watchdogd(8)</a>, <a class="Xr">watchdog(9)</a></p>
<p class="Pp"><cite class="Rs"><span class="RsT">Using the Intel ICH Family
    Watchdog Timer (WDT)</span>, <span class="RsR">Intel Application Note
    AP-725</span>, <span class="RsO">Document Number
  292273-001</span>.</cite></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Nm">ichwd</code> driver first appeared in
    <span class="Ux">FreeBSD 5.3</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<p class="Pp">The <code class="Nm">ichwd</code> driver was written by
    <span class="An">Wm. Daryl Hawkins</span>
    &lt;<a class="Mt" href="mailto:dhawkins@tamu.edu">dhawkins@tamu.edu</a>&gt;
    of Texas A&amp;M University and <span class="An">Dag-Erling
    Sm&#x00F8;rgrav</span>
    &lt;<a class="Mt" href="mailto:des@FreeBSD.org">des@FreeBSD.org</a>&gt;.
    This manual page was written by <span class="An">Dag-Erling
    Sm&#x00F8;rgrav</span>
    &lt;<a class="Mt" href="mailto:des@FreeBSD.org">des@FreeBSD.org</a>&gt;.</p>
</section>
</div>
<table class="foot">
  <tr>
    <td class="foot-date">January 3, 2026</td>
    <td class="foot-os">FreeBSD 15.0</td>
  </tr>
</table>