Device power configuration commands intercepted by virtual machine monitor

A call 52 from a user operating system (UOS) to BIOS to configure a connected device into a reduced energy consumption mode is intercepted 54 by a virtual machine monitor (VMM). The VMM determines 56 whether a service OS (SOS) is in need of the device and if so the VMM informs the UOS that the device has been configured as ordered, while allowing 60 the SOS to complete its task with the device, if the SOS is not in need of the device, or at the completion of the SOS task with the device, the VMM passes the call 58 to ACPI/BIOS to configure the device in the demanded energy consumption mode. Both the UOS and SOS include an ACPI table which may contain real and virtual device identifications.