Is my TB2 2013 MacBook Pro compatible with Thunderbolt 3? How?
 
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Is my TB2 2013 MacBook Pro compatible with Thunderbolt 3? How?  

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zejohn
(@zejohn)
New Member
Joined: 4 years ago
 

Hi all,

I'm new to the egpu game. I'm looking to add a thunderbolt 3 box to my thunderbolt 2 computer. For reference, I have the mid-2014 2.5GHz MBP.

I looked at itsage guide on the Sonnet Breakaway Box 350 which is a TB3 egpu box and he plugged it into his TB2 trash can. How did he do it? As far as I can tell, the TB3 to TB2 dongles don't work backward (at least, the reviews on Apple's official dongle say that the bi-directional compatibility feature doesn't actually work).

tl;dr: 1) Can I plug a TB3 egpu box into my TB2 computer with reduced 20gbps speeds? 2) What dongle do I use that has this bi-directional compatibility?

Thanks!

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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itsage
(@itsage)
Founder Admin
Joined: 5 years ago
 

The Apple Thunderbolt 3 (USB-C) to Thunderbolt is bidirectional. I've tested it on multiple Macs spanning all 3 Thunderbolt generations.

Forward: 2013 Mac Pro « » TB cable « » TB3-TB adapter « » TB3 enclosure

Backward: 2016 MacBook Pro « » TB3-TB adapter « » TB cable « » TB2 enclosure

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zejohn
(@zejohn)
New Member
Joined: 4 years ago
 

Okay great, and can you speak a bit to whether you'd advise daisychaining these devices? I just bought a Atikio Thunderbay that sets up 4 drives in a RAID array. I'd love to just plug in one cable for both that enclosure and the eGPU.

So it'd be: 2014mbp <-> TB2 Cable <-> TB2 to TB3 adaptor <-> eGPU box <-> (mDP to 4k 60hz monitor) <-> TB3 to TB2 <-> TB2 Cable <-> RAID array

I'm still in the return period for the RAID array. I might just get a thunderbolt 3 array for future proofing, but Apple's official dongle has a bunch of reviews saying it didn't work for the LaCie TB3 array which makes me concerned. Plus, I'll never approach the TB2 limit of 20gbps on a 4 drive RAID 5 config.  (I'll probably get a max of 700 MBps = 5.6gbps)

Taking that into consideration, will my GPU speeds be significantly affected by daisy chaining?

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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itsage
(@itsage)
Founder Admin
Joined: 5 years ago
 

Daisy chaining will negatively effect eGPU performance and therefore not recommended. Your 2014 MBP should have 2 TB ports so using both separately is the best way imo. Unless you set up an SSD RAID, there's not a big difference in using Thunderbolt enclosure vs. FW800 to warrant the cost.

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benr
 benr
(@benr)
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Joined: 5 years ago
 

I don't know your desired use case, but I personally have found the performance loss with TB2 daisy-chaining to be minimal, at least for pure rendering eGPU use.

I have a 2014 iMac with two Thunderbolt 2 ports. Plugged into one I have an Akitio Node with an Apple TB2-TB3 adapter. Plugged into the other, I have a daisy chain of: 1. Thunderbolt 2, 4-drive RAID (with two TB2 ports) -> 2. homebuilt eGPU (based on RocketStor 6361A PCB with two TB2 ports) -> 3. BlackMagic UltraStudio Mini Monitor (Thunderbolt 2 to SDI video out).

Both enclosures have identical EVGA Nvidia GPUs.

The GPU in the daisy-chained enclosure provides approximately 6.5% less performance than the one in the non-daisy-chained Akitio Node as reported by OctaneBench. Both GPUs provide well within the range of full, expected performance, equalling what people report when installing similar GPUs directly in PCI-E motherboard slots (per the Octane forums). DaVinci Resolve shows similar results.

Re-testing while the RAID is being stress-tested by the BlackMagic Disk Speed Test application barely affects eGPU performance (although the HDD RAID array is definitely not able to saturate the TB2 connection). OctaneBench results are less than 1% lower than above.

I can't speak to results for gaming use.

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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zejohn
(@zejohn)
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Joined: 4 years ago
 

Wow, thank you so much for the detailed response!! Very helpful.

Can I ask what RAID array you're using? Why do you have two eGPUs plugged in? Have you tried just testing the same eGPU enclosure in daisy-chained/non-daisy chained scenarios? 

Really appreciate all the help :). If I may - which one would you recommend?

 

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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benr
 benr
(@benr)
Eminent Member
Joined: 5 years ago
 

@zejohn 

My RAID is an OWC ThunderBay 4.

I have two eGPUs because with CUDA-based GPU rendering and DaVinci Resolve, performance scales linearly with more GPUs. Two GPUs = 2x the speed.

I'm not sure what you mean about testing in daisy-chained/non-daisy-chained scenarios – that's basically what I'm talking about, and performance is as described above. The currently daisy-chained eGPU works much the same when plugged on its own.

I'm also not sure what recommendation you're asking for: Enclosure? GPU? RAID? If your RAID is an Akitio Thunder2 Quad (I think that's what you must mean, as there is no Akitio ThunderBay, that's an OWC product), then it has two TB2 ports as mine does. I see no reason why that wouldn't daisy-chain with an Akitio Node via an Apple Thunderbolt Adapter. In my setup the RAID is first in the chain.

As to best GPU, that depends on your needs. For CUDA (GPU rendering, Resolve), get the best GTX 10xx you can afford, but be aware it's still not officially supported on OS X. Much of this forum is dedicated to the ways to make that work. For other uses – including AMD GPUs – I'm not familiar.

Hope that's helpful.

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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