According to System requirements for Windows Phone Emulator
OS : Windows 8 Pro or higher (64 - bit OS)
RAM : 4 GB or higher
For emulator : Hyper V
For WinRT Hyper-V is not required. WinRT emulator is available when VS 2012 is installed, it's part of it. So VS 2012 requirment is applicable to WinRT emulator also.