The first week of April has been insanely great for Mac users. Apple apologized that its Late 2013 Mac Pro trashcan failed to meet users’ needs. It vowed to completely redesign its next Mac Pro to make up with its core user base, the creative professionals. Two days later, Nvidia announced a beast of a graphics card, the GTX Titan Xp. It subtly dropped the news Pascal drivers for macOS would arrive within a week to support this new GPU and a whole host of GTX 10 series graphics cards.

We prepped our Mantiz Venus Thunderbolt 3 external GPU enclosure with a GTX 1080 Ti then hooked it up to a Late 2016 15″ MacBook Pro. Everything was ready to go pending the web drivers from Nvidia. April 11, 2017 marked an 11-month wait for Pascal driver support in macOS since the GTX 1080 release on May 27, 2016. This was a much longer delay than the previous seven-month wait for Maxwell drivers. All was forgiven though. Nvidia web drivers 378.05.05.05f01 are here, and they work with some visual glitches with Goalque’s automate-eGPU script to enable GTX 10 series eGPU support in macOS. This is the beta version of the drivers and hopefully these glitches will be remedied by the time the Pascal drivers are finalized.

There have been many questions and concerns about bottlenecking on eGPU implementations. Before we discuss the CPU performance, let’s assess the full path the GPU travels via the external enclosure to accelerate your ultrabook. This is a typical channel for how the external GPU communicates with the CPU:

GPU « » External Enclosure « » Thunderbolt cable « » Computer « » PCH « » CPU

Maximising TB3 eGPU performance: TB3-CPU vs TB3-PCH, how many PCIe lanes are attached?

The past five months have taught us there are frustrations in selecting the right components for your eGPU build to get the most performance. Some notable issues we’ve discovered include the 2x PCIe lane cripple with the majority of the Dell XPS line, the TI83 enclosures’ firmware Host-to-Device half-speed limit and Intel’s Thunderbolt 3 fine print (pg6) which states Thunderbolt “DATA” (i.e., PCIe traffic) is throttled down to 22Gbps. Our reports have prompted Dell to clarify its XPS laptops PCIe lanes and have encouraged external GPU manufacturers to push Intel for firmware updates.

To get the most out of an eGPU setup, you should start with a computer that is a good Thunderbolt 3 host. From the limited resources we’ve gathered to date, the Late 2016 15″ MacBook Pro is currently the best host for external GPU implementation. We found Apple attached the PCIe lanes directly to the quad-core i7 CPU in the newest 15″ MacBook Pro laptops.

This is unlike the majority of Thunderbolt 3 laptops which route the PCIe lanes through the PCH. The disadvantage of having the Thunderbolt connection through the PCH is that the PCH shares bandwidth with other internal components (e.g., PCIe flash storage, network cards, USB ports) and potentially limits the eGPU performance. Nando prepared this table explaining max bandwidth for eGPU usage on the Late 2016 MacBook Pro.

late-2016 15″ Macbook Pro late-2016 13″ Macbook Pro Touch Bar

No. of active eGPUs : bandwidth per eGPU 1: 22Gbps

2: 22Gbps/16Gbps (on alternate/same side)

3: 22Gbps on side with single eGPU, 16Gbps on side with dual eGPUs

4: 16Gbps No. of active eGPUs : bandwidth per eGPU

1: 22Gbps/16Gbps (left/right) minus other PCH devices overhead

2: 16Gbps (on alternate sides or left side only) minus other PCH devices overhead

2: 8Gbps (right side only) minus other PCH devices overhead

3: b/w 8Gbps-16Gbps depending on ports used minus other PCH devices overhead

4: 8Gbps minus other PCH devices overhead



GTX 1080 Ti Performance Testing

We wanted to test the GTX 1080 Ti Thunderbolt 3 eGPU with the Late 2016 15″ MacBook Pro to present a best-case scenario performance wise. We are using an AKiTiO Node and a Mantiz Venus TB3 external GPU enclosure for these tests. We also have a full comparison on different external enclosures in our eGPU buyer’s guide. The Unigine tests were run through the MacBook Pro‘s internal display via the ghost HDMI adapter. Here are our initial findings:

It’s an exciting time for our eGPU community. Apple is beginning to take steps in the right direction to address the power and performance needs of its pro users. At the same time Nvidia is expanding the selection of graphics cards available for eGPU implementation on Macs.

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