Overview

Today Apple releases Catalina 10.15, two years after the launch of macOS High Sierra 10.13 that introduced eGPU functionality. While there were no major changes to external GPU support in macOS, we’ve seen notable refinements in day-to-day use. Better app-level optimization, improved internal display acceleration, and Boot Screen through eGPU are the highlights of Catalina 10.15 for external graphics card users.

As more users migrate to Thunderbolt 3 Macs, the cries for eGPU support on Thunderbolt 1 & 2 machines are fading away. Thanks to our community support developers, Goalque and Mac_Editor, older Thunderbolt Macs continue to enjoy external graphics in macOS Catalina. What we’ve heard loud and clear is the omission of Nvidia graphics card support. Nvidia and Apple are acting as if they went through a bitter divorce with no option for shared custody. Users are meant to side with the brand that’s most essential to their computing needs.

Native Support

If you have a Thunderbolt 3 Mac computer, you’re in luck because this is the platform on which Apple has been building eGPU support. All you need is a MacOS-certified AMD Radeon graphics card + Thunderbolt 3 enclosure pairing that fits your needs and budget. There are eGFXs that come ready-to-go with a graphics card such as the Sonnet Breakaway Puck 560/570, Gigabyte RX 580 Gaming Box, and Blackmagic eGPU/Pro. As of fall 2019, these are Thunderbolt 3 Macs that have native eGPU support in MacOS 10.15 Catalina.

The 2018 Mac mini received preferential treatment in Catalina 10.15. Apple made changes to its firmware to allow Boot Screen Support through the eGPU-connected monitor. This feature improves usability tremendously. As a headless Mac with iGPU only, the Mac mini is a prime candidate for an external GPU. The challenge for day-to-day use so far is the need to connect a monitor directly to the Mac mini (HDMI or USB-C/Thunderbolt 3) in order to use FileVault or Boot Screen to switch between macOS and Windows. It’s reasonable to expect eGPU Boot Screen Support as a standard feature on Thunderbolt 3 and newer headless Macs going forward.

A more future-proof route is to piece together an eGPU yourself. This process takes more effort but gives you flexibility and upgradability. This is beneficial for both enthusiasts and first-timers. Enthusiasts get to have nearly full control of the features they want out of an eGPU. If you try eGPU out and decide it’s not what you expect, the GPU can be repurposed and the enclosure sold.

There is some homework to do in order to understand eGFX technology and what features are available. eGPU.io enclosure reviews go into detail on power delivery to the host computer, available expansion I/O ports, Thunderbolt 3 controller arrangement, power supply capacity and more. The options listed in the table below are currently available and best-suited for Mac computers. The ranking is based on the number of user builds in the past six months.

All Thunderbolt 3 enclosures available on the market are macOS compatible. The bigger compatibility unknown rests on the graphics card. Apple only provides native eGPU support to select AMD GPUs shown below. They are currently the families of Radeon Polaris and Vega cards. Navi cards have yet to receive drivers in the initial release of Catalina 10.15 but we expect support for them soon. As a precaution, Vega 64 GPUs demand a lot of power. Therefore the eGPU enclosure should have at least a 650W power supply. Polaris GPUs such as the RX 580 are more efficient and can work with almost all eGPU enclosures.

Once you have the whole kit together, it’s plug-and-play with a Thunderbolt 3 Mac. Hot-plug and surprise removal of the external GPU has been working since 10.13.4. Catalina 10.15 also has much better support for multiple eGPUs. In High Sierra there appeared to be a limited number of eGPU the system could handle based on the host computer’s Thunderbolt 3 controllers. Mojave 10.14 raised this multiple eGPU support to four units. Catalina 10.15 has no set limit in my testing. The bad news is the system and applications can only use up to four eGPUs concurrently.

The most exciting feature is the ability to accelerate a Mac’s internal display with the eGPU. In previous macOS builds, the external GPU could only provide acceleration to OpenGL tasks rendered through an external monitor. There’s now a checkbox to set the eGPU as the preferred graphics card for all tasks regardless of whether an external monitor is attached. This mode forces eGPU loopback to the internal display of a MacBook Pro or iMac. With that said, not all applications are optimized for eGPU use. Adobe CC 2019 has support for external and multiple GPUs in some of its apps such as Lightroom and Photoshop. As more users adopt external graphics and as drivers mature, we hope third-party software support gets better.

Community Support

Similar to macOS Mojave 10.14, Apple does not extend eGPU support to users with Thunderbolt 1/2 Macs or Nvidia graphics cards in Catalina 10.15. Our community has been relentlessly providing unofficial eGPU support for these older Macs Apple deemed unworthy. The main developers are Goalque and Mac_Editor. Without their selfless contributions eGPU for Macs would not be as popular as it is today. There are currently two primary approaches to facilitate eGPU support on older Macs. One solution is to make a Thunderbolt 1/2 Mac behave like a Thunderbolt 3 Mac. The other solution is to make an eGPU behave like an internal PCIe graphics card. Keep in mind Mac computers with the Apple T2 chip have tighter security in place. In order to implement these solutions, Secure Boot must be off and external source booting must be enabled.

Purge-Wrangler by Mac_Editor is currently the easiest solution to enable eGPU access to your Thunderbolt 1 or 2 Macs. This workaround also incorporates patches that enable compatibility with older AMD and Nvidia graphics cards as well as TI82 Thunderbolt 3 enclosures. The prerequisites are for SIP to be disabled and patching made to system files. The table below lists the Thunderbolt version of Mac computers built from early 2011 to late 2015. You can either use a Thunderbolt 2 enclosure for external graphics or use a Thunderbolt 3 enclosure via a Thunderbolt 2 cable + Apple Thunderbolt 3/USB-C to Thunderbolt adapter.

EFI automate-eGPU solution by Goalque is a cleaner approach in that all patches happen on the fly during macOS booting process. The software can be installed on an external boot volume such as a USB thumb drive or a small FAT partition of your Mac’s internal hard drive. The former is strongly encouraged so that there’s no risk of corrupting your drive and losing data. Using an external drive for each boot is not convenient, but it’s well worth the effort if you’re not willing to disable SIP and modify system files for eGPU support.

A refinement in macOS Catalina is the addition of a GPU tab in Activity Monitor. Not only does it provide a close watch on whether the eGPU is being used, but it also shows other information on the external graphics card such as brand, model, enclosure, and connected Thunderbolt 3 port. While daisy-chaining of external GPU is not recommended due to limited bandwidth through Thunderbolt 3 interface, it works regardless. I have daisy-chained three levels with the Radeon VII being at the end of the chain. For OpenCL task, the performance loss was minimal.

Boot Camp Support

Many Mac users who are interested in eGPU want to use it for gaming in Windows. We were hoping eGPU improvement in Catalina 10.15 would also mean better support for Boot Camp mode. The reality is that Apple still considers eGPU use in Windows a non-priority. We had seen beta builds of macOS Catalina 10.15 directly affect the way eGPU worked in Boot Camp. Unfortunately there’s no one clear solution. It’s easier to set up an eGPU with Boot Camp in iGPU-only Mac computers; dGPU-equipped Macs such as the 15″ MacBook Pro pose a challenge. Our Boot Camp eGPU setup guide provides more technical information and the step-by-step process for Thunderbolt 3 Mac users.

While both AMD and Nvidia have made great strides in eGPU support for Windows, Apple does not adhere to the ways Windows computers interact with Thunderbolt 3 eGPUs. I’ve been testing the 2018 15″ MacBook Pro. The Mac firmware and Apple T2 chip are big hurdles to successfully set up an external GPU in Boot Camp. The only saving grace is that it has Large Memory allocation to help with error 12 when adding an Nvidia eGPU. As seen in the screen capture, adding an AMD eGPU in Boot Camp can wreak serious havoc to the system. Both the Radeon Pro 555X dGPU and RX 580 eGPU got yellow-banged with driver conflict and lack of resource issues.

There are advances and setbacks from Microsoft’s Windows 10 Fall Update. Version 1903 continues to improve upon Windows Hybrid Graphics (introduced in 1803) that allows the external GPU to work with a discrete GPU for internal display acceleration. This is beneficial for Mac computers because Apple firmware has a tendency to disable the Intel-integrated GPU in favor of the AMD Radeon discrete GPU. Without an active iGPU, AMD XConnect and Nvidia Optimus can’t leverage eGPU acceleration to the internal display. As seen in the Graphics Settings of Windows, you can set your preference for a given software or game to use the higher-performing external graphics card. Boot Camp eGPU users need to be careful of Security Updates which take place automatically. The recommended Windows 10 1903 is OS Build 18362.295. Once your Mac is running this version, make sure to disable Windows Update in Services.

Apple has made incremental changes to Mac firmwares in each macOS build. For example Mojave and Catalina improved the 2013 Mac Pro in that they allow more Thunderbolt devices to function in operating systems other than macOS. This is a nice ability for a Mac that received no love from Apple since inception. Although not officially announced or supported, trashcan Mac users have an upgrade path from the outdated FirePro dGPUs through external enclosures in both macOS and Windows.

Closing Thoughts

Catalina 10.15 has shown positive progress for eGPU Mac users. Hot-plug capability, internal display acceleration, and multiple eGPU support can truly transform a seemingly gutless Mac mini into a powerful workstation (an affordable one at that vs. the 2019 Mac Pro). Our community remains committed to providing eGPU support for older Thunderbolt Mac users. We’re also hopeful Apple will continue to improve Mac firmwares to make eGPU in Boot Camp a more straightforward process. The jury is still out on who’s the bitch in the failed relationship of Apple and Nvidia.

One more Thing

A better-implemented Sidecar in Catalina and future macOS versions can leverage eGPU to make a hybrid touchscreen Mac. Imagine a new iPad Pro lineup that has a matching footprint to the topcase of a new MacBook Pro lineup. You would then be able to place the iPad Pro on top of the keyboard and trackpad area to use it like a drawing pad (extended display mode). Sidecar can make use of an eGPU to accelerate this drawing pad. There should also be a Sidecar app on iPadOS. This would benefit headless Macs such as the Mac mini (primary display mode). In its current implementation Sidecar display cannot be the primary display. Once we’re able to use a Sidecared-iPad as the primary display, we have ourselves a wireless touchscreen Mac. For users who would not entertain a tablet as their computer replacement, Apple can make its iPads the essential complementary accessories to Macs.

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