VirtualBox

source: vbox/trunk/doc/manual/en_US/dita/topics/changetscmode.dita@ 105791

Last change on this file since 105791 was 105335, checked in by vboxsync, 7 months ago

FE/Qt: bugref:10705. Merging r6149 from doc team's repo.

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1<?xml version='1.0' encoding='UTF-8'?>
2<!DOCTYPE topic PUBLIC "-//OASIS//DTD DITA Topic//EN" "topic.dtd">
3<topic xml:lang="en-us" id="changetscmode">
4 <title>Configuring the Guest Time Stamp Counter (TSC) to Reflect Guest
5 Execution</title>
6
7 <body>
8 <p>By default, <ph conkeyref="vbox-conkeyref-phrases/product-name"/> keeps all sources of time visible to the guest
9 synchronized to a single time source, the monotonic host time. This reflects the assumptions of many guest
10 operating systems, which expect all time sources to reflect "wall clock" time. In special circumstances it may be
11 useful however to make the time stamp counter (TSC) in the guest reflect the time actually spent executing the
12 guest. </p>
13 <p>This special TSC handling mode can be enabled on a per-VM basis, and for best results must be used only in
14 combination with hardware virtualization. To enable this mode use the following command: </p>
15 <pre xml:space="preserve">$ VBoxManage setextradata <varname>VM-name</varname> "VBoxInternal/TM/TSCTiedToExecution" 1</pre>
16 <p>To revert to the default TSC handling mode use: </p>
17 <pre xml:space="preserve">$ VBoxManage setextradata <varname>VM-name</varname> "VBoxInternal/TM/TSCTiedToExecution"</pre>
18 <p>Note that if you use the special TSC handling mode with a guest operating system which is very strict about the
19 consistency of time sources you may get a warning or error message about the timing inconsistency. It may also
20 cause clocks to become unreliable with some guest operating systems depending on how they use the TSC. </p>
21 </body>
22
23</topic>
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