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TB3 cable behaving strangely  

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HDCompatible
(@hdcompatible)
New Member
Joined: 1 month ago
 

I have a late 2016 MBP with four thunderbolt ports, a blackmagic egpu, and a dell 49" super ultrawide monitor.

I'm connecting the MBP to the BM with a 2m Chotech tb3 cable bought from amazon. From the egpu to the dell is a 1m tb3 cable ( https://www.amazon.co.uk/gp/product/B085VZ3J4D/ ). This is working well and I can play 8k video with no stutters. I use the Nasa video as a test.

When I swap the cables around, so the Chotech is between the egpu and the monitor, I get no signal on the monitor. The MBP sees the eGPU though and it charges.

I thought the chotech cable had failed so I bought another one and I got exactly the same behaviour.

Any thoughts as to why that might be the case? Could it be to do with the power supplied by the BM?

And if I buy a different 2m cable will I get the same results?

Thanks in advance for any help

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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HDCompatible
(@hdcompatible)
New Member
Joined: 1 month ago
 

An update on this. The Cable Matters 40gbps/100w cable behaved in exactly the same way. I suspect it's to do with the output signal from the balckmagic not being capable of driving a 2m cable. I don't know if that's a thing though.

 

Anyway, I returned all the 2m cables (£180 worth of cabling!) and will get another cable matters 1m. I'll just have to shuffle things around a little.

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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joevt
(@joevt)
Noble Member
Joined: 3 years ago
 

Apple has a new Thunderbolt 3 Pro Cable (2m). It's different from other 2m cables because it supports both Thunderbolt and USB-C devices (USB 3.1 gen 2 and DisplayPort signals).

Mac mini (2018), Mac Pro (Early 2008), MacBook Pro (Retina, 15-inch, Mid 2015), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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DaveBurbank
(@daveburbank)
New Member
Joined: 1 month ago
 

I'm using a Sonnet eGFX Breakaway Box with 650W Power Supply and the Gigabyte Radeon RX 5700 XT GAMING OC Graphics Card with great success on my 15 inch 2018 MacBook Pro and a late 2018 Mac Mini.

The Sonnet box comes with a eGFX Breakaway is a 1.5' (0.5m) Thunderbolt 3 cable. I think I read that longer cables will be a problem if used between the Mac and the eGPU.

Dave

 

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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HDCompatible
(@hdcompatible)
New Member
Joined: 1 month ago
 

I'll have a look at the Apple cable, thanks.

And I'll look into a 1.5m cable, that's a good idea.

As I said, the problem isn't between the mac and egpu, that seems to work whatever cable I use. The problem is between the egpu and the monitor.

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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