1. Gen2 VMs
The basic architecture of the virtual machine has not changed in a long time. Because operating systems were built to operate physical devices, all VMs emulate broadly supported hardware, such as a specific NIC card or IDE disk controller. Hyper-V in Windows Server 2012 R2 supports the concept of a totally new architecture based on modern hardware with no emulated devices. This makes it possible to add a number of new features, such as secure boot for VMs and booting off of virtual SCSI or virtual network adapters. The catch is that guest support is limited to 64-bit versions of Windows 8 and Windows Server 2012.