Apple announced support for Thunderbolt 3-based external GPUs with macOS High Sierra 10.13.4. Only select GPUs, external GPU docks, and Apple computers are supported, however, and the feature still won’t work on Windows Boot Camp.
On the computer side, 2016-and-later MacBook Pro laptops, 2017-and-later iMac desktops, and the iMac Pro are supported. On the GPU side, Apply only recommends that certain AMD Polaris and Vega graphics cards be used. Apple also notes that if you’re using a MacBook, the external GPU dock you use needs to be capable of supplying enough charging power to the laptop.
Of the gaming-focused Thunderbolt GPU docks, only the PowerColor Devil Box and Sapphire GearBox are officially recommended by Apple. The former has been tested by Apple to work with recommended GPUs up to the Vega 56, while the latter should only be used with the recommended Polaris cards. With a 500W PSU, the Devil Box is one of the most capable external GPU docks, but there’s a bunch of lower-powered units that should work fine for Polaris cards.
Performance and utilization information for external GPUs can be viewed in the macOS Activity Monitor. The full list of Apple-approved GPUs and Thunderbolt GPU docks is copied below.
For AMD Radeon RX 570, RX 580, and Radeon Pro WX 7100 graphics cards:
OWC Mercury Helios FX
PowerColor Devil Box
Sapphire GearBox
Sonnet eGFX Breakaway Box 350W
Sonnet eGFX Breakaway Box 550W
Sonnet eGFX Breakaway Box 650W
For AMD Radeon RX Vega 56:
OWC Mercury Helios FX
PowerColor Devil Box
Sonnet eGFX Breakaway Box 550W
Sonnet eGFX Breakaway Box 650W
For AMD Radeon RX Vega 64, Vega Frontier Edition Air, Radeon Pro WX 9100:
Sonnet eGFX Breakaway Box 650W