Sierra Metal is Working Well on AMD and Nvidia
With Sierra coming out shortly, Metal renders can be made on all 3 GPU platforms: Intel, AMD, and Nvidia using Fractal Architect 4 version 4.4.0.
Apple has done a very good job on the Sierra release. In general, Metal is working well, and for some older GPUs, OpenCL rendering now works again (El Capitan’s OpenCL drivers were so broken).
Both Mac OS El Capitan and Sierra support Metal rendering, but the quality of the Metal drivers varies depends on the specific GPU configuration and OS version used.
For example, on Sierra the AMD drivers are much faster than on El Capitan.
On 2013 Mac Pro, with 2 AMD GPUs, you can use both GPUs for even more speed using Metal (but OpenCL driver has a critical bug preventing usage of more than 1 GPU).
Warning – Sierra Metal may not work on your GPU
On El Capitan, my 2013 Macbook Air renders 10.5 X faster than CPU. On Sierra, the Metal compiler cannot compile the app’s kernels on the 2013 Macbook Air, resulting in no GPU rendering at all !
But 2015 Intel Iris Pro in Macbook Pro works great with Metal !
Evaluating Sierra First
Since GPU compatibility is so hit and miss, I recommend installing Sierra first on an external hard drive and trying it out on your Mac(s).
You boot off that external drive by holding down the Option key at boot and select the external drive from the list shown at boot time.
Since normal hard drives are so SLOW, I recommend the following external drive: Samsung 250 GB T3 Portable SSD. This has worked very well for me, and the cost is reasonable.
Evaluate both OpenCL and Metal
Apple’s OpenCL drivers have been very good on AMD GPUs, but don’t work at all on Intel GPUs. But that OpenCL on AMD, may be faster than Metal on AMD. So remember to try both to see what works better.