<P> In both cases, VirtualBox uses CSAM and PATM to inspect and patch the offending instructions whenever a fault occurs . VirtualBox also contains a dynamic recompiler, based on QEMU to recompile any real mode or protected mode code entirely (e.g. BIOS code, a DOS guest, or any operating system startup). </P> <P> Using these techniques, VirtualBox can achieve a performance comparable to that of VMware . </P> <P> VirtualBox supports both Intel's VT - x and AMD's AMD - V hardware - virtualization . Making use of these facilities, VirtualBox can run each guest VM in its own separate address - space; the guest OS ring 0 code runs on the host at ring 0 in VMX non-root mode rather than in ring 1 . </P> <P> VirtualBox supports some guests (including 64 - bit guests, SMP guests and certain proprietary OSs) only on hosts with hardware - assisted virtualization . </P>

Oracle virtual box and vmware are two types of