Windows ACPI Emulated Devices Table
Modern PC platforms often use devices that have known errata. In this case, the Windows family of operating systems may include mechanisms to work around these known errata whenever possible. Two example devices are the Real-Time Clock (RTC) and the ACPI Power Management (PM) timer, as implemented in some chipsets. When an operating system runs as a guest in a virtualized environment, a device may be emulated by an underlying Virtual Machine Monitor (VMM) or hypervisor. Unlike the actual device, the emulated device might not contain the errata. In this situation, special-case handling by the operating system software is unnecessary. Applying a needless work around to an emulated device can introduce unnecessary software overhead or lead to incorrect behavior when the operating system accesses device.