At least in theory, DirectX 12 supports mixed multi-adapter configurations but the problem is game developers need to implement it correctly and keep their games optimized.
The company stated that it will release the new abstraction layer as part of a comprehensive framework into the company's GitHub repository with two sample projects, one which takes advantage of the new multi-GPU tech, and one without. Exposed to this code, game developers' learning curve will be significantly reduced, and they will have a template on how to implement multi-GPU in their DirectX 12 projects with minimal effort. With this, Microsoft is supporting game developers in implementing API native multi-GPU, even as GPU manufacturers stated that while their GPUs will support EMA, the onus will be on game-developers to keep their games optimized.Via: TechPowerUp