3 Configuring virtual machines 3.4 System settings 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. 3.4.1 “Motherboard” tab 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 sys- tem, 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 chapter 1.7, Creating your first virtual machine, page 16 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 mecha- nism. This needs to be configured in detail on the command line please see chapter 8.7, VBoxManage modifyvm, page 109. 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 server, 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 Signalled Interrupts (MSI). This allows modern operating systems to address more PCI devices and no longer requires IRQ sharing. Enable I/O APIC Advanced Programmable Interrupt Controllers (APICs) are a newer x86 hard- ware 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. 43