| 1 | <?xml version='1.0' encoding='UTF-8'?>
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| 2 | <!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
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| 3 | <topic xml:lang="en-us" id="warpguest">
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| 4 | <title>Accelerate or Slow Down the Guest Clock</title>
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| 5 |
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| 6 | <body>
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| 7 | <p>For certain purposes it can be useful to accelerate or to slow down the virtual guest clock. This can be achieved
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| 8 | as follows: </p>
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| 9 | <pre xml:space="preserve">$ VBoxManage setextradata <varname>VM-name</varname> "VBoxInternal/TM/WarpDrivePercentage" 200</pre>
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| 10 | <p>The above example will double the speed of the guest clock while </p>
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| 11 | <pre xml:space="preserve">$ VBoxManage setextradata <varname>VM-name</varname> "VBoxInternal/TM/WarpDrivePercentage" 50</pre>
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| 12 | <p>will halve the speed of the guest clock. Note that changing the rate of the virtual clock can confuse the guest
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| 13 | and can even lead to abnormal guest behavior. For instance, a higher clock rate means shorter timeouts for virtual
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| 14 | devices with the result that a slightly increased response time of a virtual device due to an increased host load
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| 15 | can cause guest failures. Note further that any time synchronization mechanism will frequently try to
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| 16 | resynchronize the guest clock with the reference clock, which is the host clock if the <ph
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| 17 | conkeyref="vbox-conkeyref-phrases/product-name"/> Guest Additions are active. Therefore any time synchronization
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| 18 | should be disabled if the rate of the guest clock is changed as described above. See <xref
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| 19 | href="changetimesync.dita#changetimesync"/>. </p>
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| 20 | </body>
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| 21 |
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| 22 | </topic>
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