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modifying VM to add second processor ?

Lemmy Kilmister
Occasional Advisor

modifying VM to add second processor ?


wondering what is the best practice to add a second process to an existing VM? I was told this can create problems?

Re: modifying VM to add second processor ?


On Windows XP and later versions, the ACPI Uniprocessor HAL and the MPS Uniprocessor HAL recognize the existence of more than one processor and report the MP ID. Plug and Play detects that the computer devnode's hardware ID list has changed and moves the devnode back through the "found new hardware" detection process. Therefore, when you add a second processor, the MP files (HAL and kernels) are automatically installed, and you do not have to manually update the driver in Device Manager.

you can refer the same on the microsoft article

this should help you understand the logic behind it.

So you should be able to add the second vm after powering down the VM and going into the VM properties and increasing the number of CPUs


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Esteemed Contributor

Re: modifying VM to add second processor ?

Normally adding virtual processor to a VM once it has been installed is not recommended. It is better to start with the correct number of processors while installing.

Especially, home/client operating systems, may have some problem if you increase the number of processors after installation.

I have been able to add processors to VM after installation, just by shutting off the VM (gracefully) -> Edit Settings -> Select more CPU from drop down.

One thing you need to ensure though, not to add more processors that the OS supports.
Lemmy Kilmister
Occasional Advisor

Re: modifying VM to add second processor ?

im adding to a 2008 r2 server
Uwe Zessin
Honored Contributor

Re: modifying VM to add second processor ?

We did it this afternoon without a problem. If I remember correctly, I've read that W2008 doesn't provide a uniprocessor kernel any longer.