virtualbox.org

Hello! VirtualBox has such feature when you can set number of processors for each OS, does that mean, if I choose 1 core for Ubuntu, choose 1 core for Windows 7, and chose two for Windows 8, entire CPUs will be used in given succession, and all cores will be used? Thanks.

Only If you have quad-core CPU *and* only if you load the VMs at maximum.

Usually your VMs will not run at maximum workload, therefore you will have some extra CPU cycles.