Update:
An expert on the subject matter has clarified that DirectX 12 does indeed support mixing discrete graphics cards from different vendors, but not in SLI-like configuration. Instead, the two cards work independently to render different frames or work on the same frame in sequence by copying memory content from one card to the other through CPU memory. In fact, this option has been around since Windows 7 but it is not used much because it offers limited value compared to NVIDIA SLI or AMD CrossFire.
Original Story:
Microsoft confirmed that DirectX 12 allows Windows 10 users to install graphics cards from NVIDIA and AMD together in a SLI-like configuration.
The confirmation came only after rumors surfaced about the new feature. A screenshot provided by LinusTechTips showed them asking Microsoft about the availability of "Multi-GPU configuration" between NVIDIA and Intel cards and Microsoft responding by confirming the existence of the feature, but only between NVIDIA and AMD cards.
Microsoft is yet to release more details regarding the technical limitations and specific cards compatibility.
