TechPowerUp posted a review on the Ashes of the Singularity DirectX 12 Mixed GPU Performance
A quote from the article:
Today, the RTS game Ashes of the Singularity was released in a version which supports mixing GPUs from various vendors, even with different architecture, to provide a performance uplift similar to SLI and CrossFire. We test a selection of NVIDIA and AMD cards to investigate what to expect from the new DirectX 12 feature.Ashes of the Singularity DirectX 12 Mixed GPU Performance @ techPowerUp