Microsoft has begun seeding the Windows 10 October 2018 Update in a staggered manner and one of the important aspects of this update is that it comes with the latest version of DirectX 12 that supports DirectX Raytracing (DXR) thereby, enabling the new NVIDIA GeForce RTX cards to perform their best in raytracing-enabled games. What this also means is that cards from other companies such as AMD will also be able to take advantage of this new API.
https://www.notebookcheck.net/Windows-10-October-2018-Update-comes-with-native-DirectX-Raytracing-support.336862.0.html