I am pondering about getting a (new) notebook at some point. Apparently TB3 (officially) supports external GPU's now. The problem is that the speed of TB3 is still much lower than Pci-x... So I was wondering - and maybe someone knowledgeable can give some insight - if a notebook with TB3 and an eGPU will be a viable solution for video processing with davinci resolve and other gpu accelerated software, or how important is the "low" IO speed of TB3 vs PCI in that context?


I've looked into this recently myself, given that the MBP line is not exactly a workhorse when it comes to GPU processing.

eGPUs are actually being done now over TB2, with great success. I have a friend who purchased a similar unit to the Akitio Thunder2 (the Bizon-Tech version), put a decent GPU in it (I think it was the GTX960 or similar), and experienced almost 50% faster render time in Premiere (the latest versions of CC support GPU acceleration for encode/decode with some codecs).

The math gets a little funky, but actually this Tested article comparing PCI Express to Thunderbolt indicates that the Thunderbolt2 spec, in practice, provides almost the equivalent of a PCIe3.0 interface. The bandwidth speed lost will be minimal. Further, the article indicates that performance of the graphics card that is lost by a slower transfer speed is, for all practical intents and purposes, negligible (as little as 5% in most cases).

I'm certain that the performance gained by an eGPU box, even over TB2 on current-gen hardware, would vastly outstrip the current performance you're getting on a CPU-accellerated-only laptop.

And, the best part is, you're out only around $1500 for a box and a good graphics card.

For the record:

I don't know what notebook you're using, but I'll assume a relatively recent MBP. I'm working here from a 2014 15" Retina which happens to have dual GPUs (integrated Intel Iris and discrete GeForce GT 750M), and based strictly on CUDA cores, you'll have to pick up something in the K1200+ range if you want to see a significant improvement (the GT750M has 384 cores). However, it's relatively weak at only 2GB GDDR5 (roughly comparable to a K620 in terms of cuda cores and memory).

Improving both specs is important, particularly for 4K or RAW video. I would recommend something like a K2200 or K5000, or if you've had a good year, any of the Maxwell-class cards would be a beautiful, beautiful thing.

TechInferno - 2015 MBP + GTX970 + Akitio Thunder2 via TB2

LinusTechTips - 2012 MBP + GTX760 + Akitio Thunder2 via TB1

Bizon-Tech - Akitio-based custom enclosure for high-wattage GPUs

A useful comparison of top-end Kepler vs Maxwell NVIDIA architecture

Anecdotally, in 2014 I saw a live demo in NVIDIA's booth at NAB of what the K6000 card is capable of - at the time, mindblowing performance. They put dual K6000's in a Z820 workstation and did realtime 4k debayering of RED Raw, with scale and blur effects, in Premiere. So yeah, duh - it's a powerful card, right? Point is, you don't have to look at the latest Maxwell cards to get performance improvements in an eGPU setup - even a single quality card will provide much more efficient and expedient results than CPU-only.

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  • I looked into that option a long time ago and it involved some crude driver hacking at that time... TB2 didn't officially support eGPU while TB3 does... That's why I would hope the whole Ecosystem would get more user friendly and probably also cheaper. – Hans Meiser Apr 1 '16 at 13:32
  • Yes and yes. You're right, it's not very userfriendly. – snomsnomsnom Apr 1 '16 at 13:33
  • That being said, I'm told that on Windows it's almost plug-and-play once you get Thunderbolt to play nice. Nvidia does all the heavy lifting of making the integrated and offboard GPUs play nicely. Using windows in bootcamp mode is no joke, but a 50% performance boost - especially over a comparatively light card like the GTX970 - almost makes one want to implement the system just for rendering, although admittedly running Resolve without GPU acceleration is not pleasant. – snomsnomsnom Apr 1 '16 at 13:37
  • As for the notebook, I have two ancient mbp, 2008 and 2009... That's why have to do this research... As you mentioned the top MBP does not only have a "not to great" gpu, also I find the price of 2500€ ridiculous for what you would get in Windows notebooks nowadays. Actually I considered changing to Windows because of that which would be a huge pita, or trying to run some sort of hackintosh notebook. – Hans Meiser Apr 1 '16 at 13:39
  • The limitations of Macbook GPUs is a pretty widely known deal, and so I can easily imagine that once TB3 becomes a real thing, it won't take long for eGPU TB3 enclosures to appear. That being said, staying on the Apple platform is an expensive brand commitment, haha! Not to mention that Apple is clearly transitioning to AMD cards, which don't support CUDA, which are therefore useless for many GPU-accelerated applications. Resolve, in particular, does support OpenCL, but perhaps not as thoroughly. Adobe's products are not OpenCL compatible at all, at this time. – snomsnomsnom Apr 1 '16 at 13:50

For completeness, and in the interest of non-Mac users who may see this question in the future, I should share links to a couple other eGPU products that are commercially available today (April 2016, this will change and probably as soon as the end of the month after the NAB show in Vegas):

Alienware Graphics Amplifier - this is a fully proprietary box (with a proprietary AW connector) that performs essentially the same functionality as the Akitio or Bizon box, albeit way cooler and awesomer. And not expensive by comparison - only $200, without a graphics card.

Razer Blade Stealth + Core - this is a TB3/USB-C protocol in a sleek little enclosure for $500 empty. Compatible with laptops sporting the USB-C protocol, this is a great option going forward for many laptop users. Polygon did a great writeup about it.

All in all, you're still out at least $1500 for a solid external GPU solution, but there are some nice options out there.

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