From what I have read DX12 is basically DX11 with mantle baked in. Some improvements over 11, but not radically different. Because of this, all DX11 cards are capable of running with DX12. Fermi, Kepler and Maxwell (Nvidia 500 series forward) will be called DX12 ready cards. Since DX11 is on Win7, there is no reason DX12 can't be moved to Win7, but MS does want to push dat Windows H8 point done.