with Mac Pro 2013 (or any Mac with Thunderbolt port), you need High Sierra, an eGPU box with Thunderbolt 2, or 3 with Apple adapter:https://www.apple.com/shop/product/MMEL ... -2-adapter
You can use the internal AMD GPU for system/monitor/OpenGL, while the external GPU is used only for CUDA rendering, at full power and with all the available VRAM per GPU.
At the following link you can find an extensive guide about eGPU solutions via Thunderbolt under Mac:The Beginner’s eGPU Setup Guide for Mac
Here are a couple of eGPU solutions used by other Mac Octane users:https://www.sonnettech.com/product/egfx ... y-box.htmlhttps://www.razer.com/gaming-laptops/razer-core-v2https://www.akitio.com/expansion/thunder3-pcie-boxthe last solution needs an external PSU to work, as explained here:viewtopic.php?f=9&t=43439&start=170#p276341
At the following link you can find the OctaneBench results of the currently supported GPUs:https://render.otoy.com/octanebench/res ... ingleGPU=1New Volta and Touring architecture RTX 2070/2080/2080ti are not currently supported under Mac.
From the software side, you need to follow the steps described at the following link:for High Sierra
At the end of the process, you can finally install Octane, and start rendering.Note that tat the moment it is not possible to update to Mojave:https://devtalk.nvidia.com/default/topi ... cos-10-14/
With Mac Pro 2009 (like mine), you need to upgrade to Sierra or High Sierra, then use the GT 120 for display, and add a couple of Pascal GPUs, like 1060/1070 without external power supply:
Or add a couple of 1080ti with external power supply:https://youtu.be/5FWXgQSokF4