Today in 2015, my guess is that only in 1 in 4 customers have Macs whose GPUs are compatible with FA 4 GPU OpenCL rendering. Before Mavericks, almost 100% of Macs (those with Nvidia or ATI GPUs) could use FA 2’s GPU rendering.
There are multiple OpenCL driver issues causing this and frankly there is nothing that can be done to fix it as a small app developer.
That is why free GPU Trial was put in the app and why GPU rendering is an optional purchase. We did not want customers to feel they spent money on a broken feature, especially when we have no ability to fix the underlying bugs in Mac OS X’s OpenCL drivers.
GPU from iMac Retina R9 M295X works.
CPU Rendering works on ALL Macs, here we are talking about OpenCL GPU rendering.
2013 Macbook Pro D700 GPUs works
2012 15″ Retina Macbook Pro Nvidia 650GTM works
2011 15″ Retina Macbook Pro AMD 6550M works
These Macs don’t work with GPU rendering ====
2014 15″ Retina macbook Pro Nvidia 750GTM
2010 15″ Macbook Pro Nvidia 330M
All Macs not having either an Nvidia or AMD(ATI) GPU.