Fractal Architect version 4.5.0 submitted to Apple today (Dec 14, 2016) makes it possible to use either OpenCL or Metal GPU rendering with Intel processors. This capability requires Mac OS Sierra.
With Mac OS Sierra, it seems that all Intel CPUs (2013 and later) having Intel HD, Intel Iris, or Intel Iris Pro GPUS can now take advantage of either OpenCL or Metal rendering for HUGE speed increases. For example, a 2013 MacBook Air gets approx. a 9x speed increase ! That is like a baby going from crawling to Olympic sprinting.
On Macbook Pros and iMacs having both a discrete AMD GPU and an Intel processor with its integrated GPU, you can use both GPUs together for rendering. This gives you almost twice the rendering speed !
Thank you Apple for giving us great OpenCL and Metal drivers on Mac OS Sierra !!
Note: Older versions of Mac OS and Macs produced in 2012 or earlier may have compatibility problems. (But CPU rendering works fine.)