virtualbox.org

Hi all,
Does no. of CPU option correspond to physically no. of CPU available or to no. of cores also.
I mean if I am running on a quad core CPU in the host OS then can I change the no. of CPU value to 2/3.

And can I change this option or is it advisable to change it once the guest OS is up and running?

Thanks,
Pratik

You can't change it when a VM is running. Would be a bit weird don't you think? Adding an additional CPU or core while a PC is running.

If you meet the hardware requirements for SMP, then it's the cores it's talking about. Having two CPUs allows you to give the VM two processors. Having two quad core CPUs allows you to give the VM 8 processors, but that's not advised. Always leave one core for the Host, so the VM can't bring down the system.