Last year when Apple first announced macOS High Sierra, we learned that Mac users would finally be getting official support for external GPUs. It has taken a while, but that support has finally arrived, allowing users to hook up a bunch of different GPUs to Mac systems using the Thunderbolt 3 port. Unfortunately, since this Apple, there are also a number of limitations in place.
Apple is only officially supporting a select number of graphics cards for use externally on macOS. Since Apple has made the switch to exclusively AMD GPUs, the company will only be supporting Radeon cards for external support. However, last year Nvidia did make GTX 10-series drivers available on macOS, so there will be work arounds in place.
External GPUs won't work while using Windows Boot Camp to dual boot on macOS. Apple is also relying on developers to enable eGPU support in apps for it to work. In most use cases, this should be fine, with eGPUs supporting 3D Games, VR applications and professional apps like video editing and rendering suites.
The other final hurdle users will have to jump through is ensuring their Mac is actually compatible. External GPUs rely on Thunderbolt 3 to work, so machines like the 2013 Mac Pro won't have support, but MacBook Pros from the last two years will. iMacs released in the last year will also be supported.
KitGuru Says: The number of hurdles in place does seem a bit silly, particularly since Hackintosh systems have become much more stable over the last few years. My PC currently has macOS and Windows 10 dual-booted, with an Intel Core i7-8700K and a GTX 1080Ti. Still, hopefully over time, Apple will open up official support to more GPUs.