| 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>
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| 8 | For certain purposes it can be useful to accelerate or to slow
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| 9 | down the virtual guest clock. This can be achieved as follows:
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| 10 | </p>
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| 11 | <pre xml:space="preserve">$ VBoxManage setextradata <varname>VM-name</varname> "VBoxInternal/TM/WarpDrivePercentage" 200</pre>
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| 12 | <p>
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| 13 | The above example will double the speed of the guest clock while
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| 14 | </p>
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| 15 | <pre xml:space="preserve">$ VBoxManage setextradata <varname>VM-name</varname> "VBoxInternal/TM/WarpDrivePercentage" 50</pre>
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| 16 | <p>
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| 17 | will halve the speed of the guest clock. Note that changing the
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| 18 | rate of the virtual clock can confuse the guest and can even
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| 19 | lead to abnormal guest behavior. For instance, a higher clock
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| 20 | rate means shorter timeouts for virtual devices with the result
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| 21 | that a slightly increased response time of a virtual device due
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| 22 | to an increased host load can cause guest failures. Note further
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| 23 | that any time synchronization mechanism will frequently try to
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| 24 | resynchronize the guest clock with the reference clock, which is
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| 25 | the host clock if the Oracle VM VirtualBox Guest Additions are active.
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| 26 | Therefore any time synchronization should be disabled if the
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| 27 | rate of the guest clock is changed as described above. See
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| 28 | <xref href="changetimesync.dita#changetimesync"/>.
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| 29 | </p>
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| 30 | </body>
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| 31 |
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| 32 | </topic>
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