What you need to know about the Mac, Thunderbolt 3, and external GPUs

MacBook Pro + Thunderbolt 3 + NVIDIA Titan Xp = why doesn't this work? ☹️

There's no denying that graphics performance in current Macs isn't the best. There are always tradeoffs to make, and Apple tends to err on the side of battery life and heat management over raw performance. That led to the new MacBook Pro being equipped with the latest AMD GPUs, even if there were doubly-more-powerful NVIDIA chips available. But there's another option, at least in theory: the external GPU. Plug in an enclosure via a Thunderbolt 3 cable and voilà you've got desktop-class graphics performance for your slim MacBook.

... Almost

Except there were problems. The first was that NVIDIA hadn't released Mac drivers for their latest and most powerful GTX 10-series and Titan GPUs, which meant that any Mac user that wanted to use an external NVIDIA graphics card was saddled with at best a year-old option. Thankfully, NVIDIA is ending that issue by issuing drivers for the top-end Pascal-powered GPUs.

The bigger problem, however, is on the Apple side. Thunderbolt 3 offers an absurd 20Gbps of data throughput in each direction, and there are external enclosures capable of holding, powering, and connecting even the fancy new NVIDIA Titan Xp with its 12 teraflops of graphics performance. The problem is a lack of full support from macOS. There have been hints of eGPU support in betas of macOS Sierra (with some tweaking required), but as of even the latest 10.12.3 public release it's still not widely available. And the support that Apple has been playing with has been limited — the GPUs aren't yet able to send data back to the MacBook, so you'll have to run it out to an external display connected to the GPU.

Image via eGPU.io.

The benefits of hooking up a desktop-class GPU to a MacBook cannot be understated, at least for those that need that kind of power. If you're a gamer, you'll want one for vastly-improved graphics. Sure, a 15-inch MacBook Pro can drive a pair of 5K displays, but if you try and play any graphically intense game at full resolution it'll grind to a halt. The bigger potential market is with people who need the massive power of a GPU for other tasks.

Modern graphics cards excel at parallel computing — they were designed to render a huge number of assets all at once in real time for games, and that means that cards like the NVIDIA Titan Xp are equipped with a mind-boggling 3,840 processing cores. Modern computers can leverage all of that computational power as additional processing power for tasks other than putting pixels on a monitor. GPUs are used in everything from rendering video from Final Cut to 3D rendering in 3ds Max to applications in defense, medical imaging, climate study, and structural mechanics. Heck, Google even uses GPUs as processors in their servers.

As somebody who does both video and 3D rendering on my MacBook Pro, I've been watching the development and struggles of eGPU support on macOS with great hope and frustration. Even Apple has acknowledged that there's interest — asked specifically about external GPUs, Apple senior vice president of Software Engineering Craig Federighi said, "I think they have a place."

Coupled with the news that Apple is approaching the next-generation Mac Pro from a more customizable route, NVIDIA's newfound support for macOS on their top-end GPU is encouraging. We're still a long way off from seeing whatever Apple has in the works, but we could be looking at a future of top-end — and upgradeable — graphics performances for Macs. And that's something we haven't seen since 2013.

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