I noticed the new screen below and appears in Windows Server 2012 R2 Preview.

Virtual machine generation determines the virtual hardware and functionality presented to the virtual machine.

In Hyper-V within Windows Server 2012 R2 there are two supported virtual machine generations, generation 1 and generation 2 virtual machines.

Generation 2 virtual machines will be presented with a simplified virtual hardware model and supports Unified Extensible Firmware Interface (UEFI) firmware instead of BIOS based firmware.

Additionally the majority of emulated (legacy) devices have been removed from generation 2 virtual machines.

 

Generation in Hyper-V

  • Generation 1 - This virtual machine generation provides the same virtual hardware to the virtual machine as in previous versions of Hyper-V.
  • Generation 2 - This Virtual machine generation provides the following new functionality to a virtual machine:
    • Secure Boot (enabled by default)
    • Boot from a SCSI virtual hard drive
    • Boot from a SCSI virtual DVD drive
    • PXE boot using a standard network adapter
    • UEFI firmware support
    • IDE drives and legacy network adapter support has been removed