Porting complexity is still non-trivial, and then you need people who understand multiple bare metal APIs. The architectures are all based off Mantle, but Open

Porting complexity is still non-trivial, and then you need people who understand multiple bare metal APIs. The architectures are all based off Mantle, but OpenGL 3.3 and DX10 were very similar in their hay day, and porting was still fairly limited (you can still partially blame the horrible adoption of the 3.x series that took so long to take off).