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<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>
