Available article translations:

Boot Camp-based Windows virtual machine cannot boot with more than 2Gb of RAM

  • Parallels Desktop 9 for Mac Standard Edition


  • I am unable to boot my Boot Camp-based Windows virtual machine if I set more than 2Gb of RAM for the virtual machine.

  • Virtual machine is booting fine with up to 2Gb of RAM.


The MBR of Boot Camp-based Windows OS has been modified in order to enable SATA AHCI mode in Boot Camp-based Windows virtual machine. With these modifications on boot SATA PCI memory bar is relocated to the hardcoded location which may not comply with an arbitrary memory map. For example, it does not comply with the one of the Parallels virtual environment.


Please repair Windows MBR using bootrec.exe tool available in Repair Environment of Windows installation image.

NOTE: MBR should be restored inside the virtual machine, because otherwise AHCI mode would be disabled in Bootcamp itself, both making it impossible to boot to Bootcamp and the virtual machine.

For Windows XP:

Please check FIXMBR section in Description of the Windows XP Recovery Console for advanced users

For Windows Vista or Windows 7:

Use Bootrec.exe in the Windows RE to troubleshoot startup issues

For Windows 8 (8.1):

  1. Connect the Windows 8.1 installation ISO (or DVD) to the virtual machine. Make the virtual machine boot from it.
  2. Launch the virtual machine.
  3. Instead of starting the installation in the corresponding dialog use the "Repair your computer" option.
  4. Navigate as follows: Troubleshoot -> Advanced Options -> Command Prompt
  5. In the command prompt type:

    bootrec /fixmbr
  6. Shutdown the virtual machine. Disconnect installation media.
  7. The Bootcamp virtual machine should boot with more than 2GB memory fine.

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