Adding a Second CPU to an Existing Windows VM

Written by:

If you’ve ever installed Windows as a VM with only one CPU only to find out that you need two you’re in luck!  Here is a guide on how to do it. (Note that multiple CPUs are only supported by some virtualization programs such as VMWare Server, VMWare ESX and Microsoft Virtual Server)

  1. Shutdown the VM
  2. Take a snapshot/backup of the VM just in case anything goes wrong.
  3. In the virtual machine manager add a second CPU (This step will vary depending on the virtualization technology used)
  4. Turn the VM back on (The VM should boot up without any problems albeit with one CPU)
  5. Go to the Device Manager
    1. Expand Computer
    2. Right click ACPI Uniprocessor PC (the actual name may be slightly different) and click Update Driver
    3. If it asks to search the internet for drivers select Yes
    4. Select Install from a list or specific location
      1. Click Next
    5. Select Don’t search.  I will choose the driver to install
      1. Click Next
    6. Select ACPI Multiprocessor PC
      1. Click Next
    7. Finish the wizard
  6. Reboot the VM
    1. Once the VM is back up there should be two CPUs visible in the Task Manager

That’s it!  Enjoy your second CPU and all the performance it brings.

-Lee

Posted on July 30th, 2009 in Technology, Tips & Tricks.