The "System" category groups various settings that are related to the basic hardware that is presented to the virtual machine.
Note
As the activation mechanism of Microsoft Windows is sensitive to hardware changes, if you are changing hardware settings for a Windows guest, some of these changes may trigger a request for another activation with Microsoft.
On the "Motherboard" tab, you can influence virtual hardware that would normally be on the motherboard of a real computer.
- Base memory
-
This sets the amount of RAM that is allocated and given to the VM when it is running. The specified amount of memory will be requested from the host operating system, so it must be available or made available as free memory on the host when attempting to start the VM and will not be available to the host while the VM is running. This is the same setting that was specified in the "New Virtual Machine" wizard, as described with guidelines under Section 1.7, “Creating your first virtual machine” above.
Generally, it is possible to change the memory size after installing the guest operating system (provided you do not reduce the memory to an amount where the operating system would no longer boot).
- Boot order
-
This setting determines the order in which the guest operating system will attempt to boot from the various virtual boot devices. Analogous to a real PC's BIOS setting, VirtualBox can tell a guest OS to start from the virtual floppy, the virtual CD/DVD drive, the virtual hard drive (each of these as defined by the other VM settings), the network, or none of these.
If you select "Network", the VM will attempt to boot from a network via the PXE mechanism. This needs to be configured in detail on the command line; please see Section 8.8, “VBoxManage modifyvm”.
- Chipset
-
Here you can select which chipset will be presented to the virtual machine. Before VirtualBox 4.0, PIIX3 was the only available option here. For modern guest operating systems such as Mac OS X, that old chipset is no longer well supported. As a result, VirtualBox 4.0 introduced an emulation of the more modern ICH9 chipset, which supports PCI express, three PCI buses, PCI-to-PCI bridges and Message Signaled Interrupts (MSI). This allows modern operating systems to address more PCI devices and no longer requires IRQ sharing. Using the ICH9 chipset it is also possible to configure up to 36 network cards (up to 8 network adapters with PIIX3). Note that the ICH9 support is experimental and not recommended for guest operating systems which do not require it.
- Pointing Device
-
The default virtual pointing devices for older guests is the traditional PS/2 mouse. If set to USB tablet, VirtualBox reports to the virtual machine that a USB tablet device is present and communicates mouse events to the virtual machine through this device. The third setting is a USB Multi-Touch Tablet which is suited for recent Windows guests.
Using the virtual USB tablet has the advantage that movements are reported in absolute coordinates (instead of as relative position changes), which allows VirtualBox to translate mouse events over the VM window into tablet events without having to "capture" the mouse in the guest as described in Section 1.8.2, “Capturing and releasing keyboard and mouse”. This makes using the VM less tedious even if Guest Additions are not installed.[12]
- Enable I/O APIC
-
Advanced Programmable Interrupt Controllers (APICs) are a newer x86 hardware feature that have replaced old-style Programmable Interrupt Controllers (PICs) in recent years. With an I/O APIC, operating systems can use more than 16 interrupt requests (IRQs) and therefore avoid IRQ sharing for improved reliability.
Note
Enabling the I/O APIC is required for 64-bit guest operating systems, especially Windows Vista; it is also required if you want to use more than one virtual CPU in a virtual machine.
However, software support for I/O APICs has been unreliable with some operating systems other than Windows. Also, the use of an I/O APIC slightly increases the overhead of virtualization and therefore slows down the guest OS a little.
Warning
All Windows operating systems starting with Windows 2000 install different kernels depending on whether an I/O APIC is available. As with ACPI, the I/O APIC therefore must not be turned off after installation of a Windows guest OS. Turning it on after installation will have no effect however.
- Enable EFI
-
This enables Extensible Firmware Interface (EFI), which replaces the legacy BIOS and may be useful for certain advanced use cases. Please refer to Section 3.14, “Alternative firmware (EFI)” for details.
- Hardware clock in UTC time
-
If checked, VirtualBox will report the system time in UTC format to the guest instead of local (host) time. This affects how the virtual real-time clock (RTC) operates and may be useful for Unix-like guest operating systems, which typically expect the hardware clock to be set to UTC.
In addition, you can turn off the Advanced Configuration and Power Interface (ACPI) which VirtualBox presents to the guest operating system by default. ACPI is the current industry standard to allow operating systems to recognize hardware, configure motherboards and other devices and manage power. As all modern PCs contain this feature and Windows and Linux have been supporting it for years, it is also enabled by default in VirtualBox. It can only be turned off on the command line; see Section 8.8, “VBoxManage modifyvm”.
Warning
All Windows operating systems starting with Windows 2000 install different kernels depending on whether ACPI is available, so ACPI must not be turned off after installation of a Windows guest OS. Turning it on after installation will have no effect however.
On the "Processor" tab, you can set how many virtual CPU cores the guest operating systems should see. Starting with version 3.0, VirtualBox supports symmetrical multiprocessing (SMP) and can present up to 32 virtual CPU cores to each virtual machine.
You should not, however, configure virtual machines to use more CPU cores than you have available physically (real cores, no hyperthreads).
On this tab you can also set the "CPU execution cap". This setting limits the amount of time a host CPU spends to emulate a virtual CPU. The default setting is 100% meaning that there is no limitation. A setting of 50% implies a single virtual CPU can use up to 50% of a single host CPU. Note that limiting the execution time of the virtual CPUs may induce guest timing problems.
In addition, the "Enable PAE/NX" setting determines whether the PAE and NX capabilities of the host CPU will be exposed to the virtual machine. PAE stands for "Physical Address Extension". Normally, if enabled and supported by the operating system, then even a 32-bit x86 CPU can access more than 4 GB of RAM. This is made possible by adding another 4 bits to memory addresses, so that with 36 bits, up to 64 GB can be addressed. Some operating systems (such as Ubuntu Server) require PAE support from the CPU and cannot be run in a virtual machine without it.
With virtual machines running modern server operating systems, VirtualBox also supports CPU hot-plugging. For details about this, please refer to Section 9.5, “CPU hot-plugging”.
On this page, you can determine whether and how VirtualBox should use hardware virtualization extensions that your host CPU may support. This is the case with most CPUs built after 2006.
You can select for each virtual machine individually whether VirtualBox should use software or hardware virtualization.[13]
In most cases, the default settings will be fine; VirtualBox will have picked sensible defaults depending on the operating system that you selected when you created the virtual machine. In certain situations, however, you may want to change these preconfigured defaults.
Advanced users may be interested in technical details about software vs. hardware virtualization; please see Section 10.3, “Hardware vs. software virtualization”.
If your host's CPU supports the nested paging (AMD-V) or EPT (Intel VT-x) features, then you can expect a significant performance increase by enabling nested paging in addition to hardware virtualization. For technical details, see Section 10.7, “Nested paging and VPIDs”.
Starting with version 5.0, VirtualBox provides paravirtualization
interfaces to improve time-keeping accuracy and performance of guest
operating systems. The options available are documented under the
paravirtprovider option
in Section 8.8, “VBoxManage modifyvm”. For further details on
the paravirtualization providers, please refer to
Section 10.4, “Paravirtualization providers”.
[12] The virtual USB tablet was added with VirtualBox 3.2. Depending on the guest operating system selected, this is now enabled by default for new virtual machines.
[13] Prior to VirtualBox version 2.2, software virtualization was the default; starting with version 2.2, VirtualBox will enable hardware virtualization by default for new virtual machines that you create. (Existing virtual machines are not automatically changed for compatibility reasons, and the default can of course be changed for each virtual machine.)