Warning: This isn't officially supported by Apple yet, and a bit hacky. But if you want top-tier graphics performance, here's what you need to do.
Updated April 2017: NVIDIA's Pascal drivers are now available for download on the Mac, if you plan to use a Titan Xp as an external GPU.
External GPUs are in the news lately, what with NVIDIA's announcement offering macOS drivers for its Titan Xp, so we thought we'd take a second to explain what, exactly, an external GPU is — and how you'd go about getting one.
External GPUs: Supercharging gaming and video production
All Macs have a CPU, which provides the primary processing power for your computer. But in addition, they have a GPU — a graphics processing unit — designed to drive your computer's screen, external displays, and visuals.
GPUs are what sell high-end Windows gaming laptops and desktops: They keep your favorite game flawless, your external display running smoothly, and visual effects rendering speedy.
But all that power comes at the expense of battery and optimization: Heavy-duty GPUs are frequent power hogs with lots of fan noise and problematic battery life.
As such, Apple has historically trended toward putting in GPUs that balanced power with optimization: great for your laptop's battery life; not so great for gamers or visual effects artists.
Enter external GPUs: Like external hard drives, these essentially allow you to stick a GPU in a Thunderbolt housing, where you can then connect it to your computer; from there, when you run games and visual apps optimized for that GPU you should see significant performance improvements. Awesome, right? Well, almost.
The cons of an external GPU on your Mac
Here's the issue: Macs don't officially support external GPUs. That's not to say you can't use an external GPU, only that Apple Support won't bail you out if you do something that doesn't agree with your Mac. Proceed at your own risk, here be dragons, et cetera.
In addition, should you decide to use an external GPU, there are only a handful of Thunderbolt enclosures and graphics cards with appropriate Mac drivers — you can't just pick an arbitrary graphics card you'd like to attach to your Mac.
How to use an external GPU with your Mac
Thankfully, you don't have to venture into the void without guidance: The eGPU.io community has put together a huge array of helpful how-tos and setup guides for interested users — I'm looking forward to using their startup guide and forums to make a Thunderbolt 3 eGPU for my MacBook Pro.
Other questions about external GPUs? Let us know below.