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<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
<topic xml:lang="en-us" id="warpguest">
<title>Accelerate or Slow Down the Guest Clock</title>
<body>
<p>For certain purposes it can be useful to accelerate or to slow down the virtual guest clock. This can be achieved
as follows: </p>
<pre xml:space="preserve">$ VBoxManage setextradata <varname>VM-name</varname> "VBoxInternal/TM/WarpDrivePercentage" 200</pre>
<p>The above example will double the speed of the guest clock while </p>
<pre xml:space="preserve">$ VBoxManage setextradata <varname>VM-name</varname> "VBoxInternal/TM/WarpDrivePercentage" 50</pre>
<p>will halve the speed of the guest clock. Note that changing the rate of the virtual clock can confuse the guest
and can even lead to abnormal guest behavior. For instance, a higher clock rate means shorter timeouts for virtual
devices with the result that a slightly increased response time of a virtual device due to an increased host load
can cause guest failures. Note further that any time synchronization mechanism will frequently try to
resynchronize the guest clock with the reference clock, which is the host clock if the <ph
conkeyref="vbox-conkeyref-phrases/product-name"/> Guest Additions are active. Therefore any time synchronization
should be disabled if the rate of the guest clock is changed as described above. See <xref
href="changetimesync.dita#changetimesync"/>. </p>
</body>
</topic>
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