One of the biggest changes coming thanks to DirectX 12 will be the eventual ability to combine multiple GPUs to boost PC performance.
AnandTech reports "DirectX 12’s explicit controls extend to multi-GPU rendering as well. It is now up to developers to decide if they want to use multiple GPUs and how they want to use them. And with explicit control over the GPUs along with the deep understanding that only a game’s developer can have for the layout of their rendering pipeline, DirectX 12 gives developers the freedom to do things that could never be done before."
The example given is the Star Swarm demo from developer Oxide Games, ahead of its full retail release in 2016 as Ashes of the Singularity. Oxide has taken the underlying Nitrous engine and using it as a testbed for DirectX 12 technologies to make a new build of the game.
The new build is the first game demo created for DirectX 12's multi-GPU Explicit Multi-Adapter functionality. The EMA allows DirectX 12 to pair dissimilar GPUs which boost productivity.
Ashes of the Singularity was recently added to Steam Early Access, you can find out more about Oxide Games wants to get out the Steam trial here.
You can read more in AnandTech's report.