Microsoft's DirectX 12 API is shaping up to be one of the greatest software-based advancement in PC gaming in a very long time. The new API not only promises massive gains in terms of performance and power efficiency, but will also bring great improvements in terms of hardware compatibility.
Previous rumors already revealed DX12 promises to perform memory stacking on CrossFireX and SLI multi-GPU systems and now Tom's Hardware breaks news that it will be possible to let GPUs from multiple vendors work together. With DX12, it should finally become possible to let NVIDIA GPUs work in tandem with AMD GPUs to render the same game - the same frame, even!
This is especially interesting as it allows you to leverage the technology benefits of both of these hardware platforms if you wish to do so. If you like Nvidia's GeForce Experience software and 3D Vision, but you want to use AMD's TrueAudio and FreeSync, chances are you'll be able to do that when DirectX 12 comes around. What will likely happen is that one card will operate as the master card, while the other will be used for additional power.
What we're seeing here is that DirectX 12 is capable of aggregating graphics resources, be that compute or memory, in the most efficient way possible. Don't forget, however, that this isn't only beneficial for systems with multiple discrete desktop GPUs. Laptops with dual-graphics solutions, or systems running an APU and a GPU will be able to benefit too. DirectX 12's aggregation will allow GPUs to work together that today would be completely mismatched, possibly making technologies like SLI and CrossFire obsolete in the future.
The catch is that lots of the optimization work for spreading the workloads is left to the game developers, but the new features of DX12 promise to be easier to implement than older APIs.