AMD's Robert Hallock, head of Global Technical Marketing, confirmed to ComputerBase that the Graphics Core Next (GCN) GPUs don't have full DirectX 12 feature level support.
The firm's current high-end cards like the Radeon R9 290(X) and Radeon R9 285 are limited to DirectX 12 feature level 12_0. Basically, all AMD GCN 1.1 and GCN 1.2 based cards have DX12 Feature Level 12_0 support and everything based on GCN 1.0 is limited to DX12 Feature Level 11_1.
It's unknown which feature level is supported by the upcoming Fiji, perhaps that will be the only fully DX12 compliant card in AMD's lineup. But even that is a bit unsure at the moment as Hallock mentioned that DX12 Feature Level 12.1 support isn't important for them, claiming anything relevant to games is included in feature level 11_1 and 12_0.
The reference DirectX 12 API (Feature Level 11_0) has performance targeted features while the other two level deliver graphical improvement and this is what really matters in improving the games visually. The feature level 12_0 comes with Tiled Resources, Typed UAV Access and Bindless Textures support. Feature Level 12_1 has the Raster Order Views, Conservative Raster and Volume Tiled Raster enabled on the API.
It seems that at least marketing-wise, NVIDIA has the upper hand here as the firm's GeForce 900 series already supports DX12 feature level 12_1, but anything else from the GeForce 400 to GeForce 700 series is DX12 feature level 11_1.
What this actually means and if it's relevant at all remains to be seen, especially because this news means the current-generation of consoles doesn't support DX12 feature level 12_1 either.