Optimization levels under Virtual PC

Optimization levels under Virtual PC

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On a running virtual machine (under Virtual PC) you can see the optimization level being used by selecting 'Properties' off of the 'Action' menu - and then going to the 'Advanced' tab.  There are three possible optimization levels:

  1. None: You should only ever see this if you are using the '-disableopt' command line option - and you would only ever want to do this for debugging purposes.

  2. User mode optimization enabled: This is the default mode of operation for virtual machines.  User mode code (or ring 3) is run directly on the processor - but kernel mode code (or ring 0) is handled inside of a binary translator.

  3. User and kernel mode optimizations: In this mode both user and kernel mode code is run directly on the processor.  This mode is only enabled on certain operating systems (windows NT, 2000, XP, 2003, Vista) once Virtual Machine Additions have been loaded.


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  • If ring 0 code is allowed to run directly on processor, how can VPC prevent the guest from using the real hardware directly ?
  • We're watching you...
  • We use ring compression to run the guest ring 0 code at ring 1.  Check out my channel 9 video:


  • Amazing that you can get (practically) any OS, that thinks its at ring 0, to run at ring 1.
  • Any chance to get 'Windows 7 Professional SP1' from MSDN work as 3. User and kernel mode optimization ? I have tried latest VM Additions version 13.823 and it still does not work. Windows 7 is the only x86 edition you can install Visual Studio 11 preview into :-/ Windows Server 2008 SP2 runs fine with both optimizations in Virtual PC.

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