For anyone interested in 3D Graphics and Rendering, there looks to be some good news on the way when Blender 2.79 gets released for owners of AMD Graphics Cards.
Two key features will help improve rendering times and productivity.
Blender 2.79 includes:
1. New AMD OpenCL optimizations
2. Faster AMD OpenCL rendering and feature parity with NVidia CUDA.
I am seeing significant performance improvements in Blender 2.79 Release Candidate 2 so far running on a range of testcases, both blender benchmarks and my own testcases.
I was unable to run Dual R9 Nano GPU's in Blender version 2.78c. This works for my cards in Version 2.9 Release Candidate 2.
I am seeing performance improvements over and above just the fact that I can run renders with two GPU's instead of one.
I understand this is not a production version of Blender but you might want to download it and take a look.
You can get information on the Blender 2.79 Release Candidate 2 code here:
Dev:Ref/Release Notes/2.79 - BlenderWiki
If anyone does decide to test the Blender 2.79 Release Candidate 2 and is lucky enough to have an RX Vega 64 I would be grateful if you would give it a try, and also give some feedback on use of High Bandwidth Cache Controller for large rendering jobs where the native GPU Memory Capacity (in my case 4GB, but in Vega Case 8GB or 16GB) is a problem.