How is the Apple Thunderbolt 2 to 3 adapter bidirectional?

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How is the Apple Thunderbolt 2 to 3 adapter bidirectional?

In the description for this product it says:

“This adapter is bidirectional, which means you can use it to connect Thunderbolt 3 devices to a Mac that has a Thunderbolt or Thunderbolt 2 port. In that case, the Mac device must be using macOS Sierra or later, and the device using Thunderbolt 3 must provide its own power.”

I don’t understand how you this works? How can you connect it to a Thunderbolt 2 port when in all the pictures for the product it only has a thunderbolt 3 connector on one side and a thunderbolt 2 port on the other? 🤔

Many thanks

Posted on Jul 20, 2024 3:41 PM

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Answer 1

Tesserax

Level 10

157,902 points

Jul 20, 2024 8:26 PM in response to MiniMum97

Ok, let's step back for a moment. Hopefully, I can clear up some things about computer ports, and associated cables.

First, there are standards. These define the ports capabilities. For USB, they are USB 1.x, 2.x, 3.x, etc. For Thunderbolt, they are Thunderbolt 1, 2, 3, & now 4. Each of these standards define things like the data throughput and power capabilities that a port can support.
Second, there are physical port types. These define what a port looks like. For USB, they are USB-A, -B, -C. For Thunderbolt, this is where things get a bit more confusing. For Thunderbolt 1 & 2, they use DisplayPort type ports. For Thunderbolt 3 & 4, they use USB-C type ports.

So, going back to your Mac. If it only supports Thunderbolt 1 or 2 connections, then it would be equipped with DisplayPort type ports. Most likely, it would also have a USB-A type port. If you can provide us with the exact models of each of your Macs, I can verify what they have.

Since you are trying to connect two Macs to allow one to access the drive of the other, are you trying to use Target Disk Mode for this? If so, is one of these Macs a Silicon-based Mac?

Transfer files between two Mac computers using target disk mode - Apple Support
Transfer files between a Mac with Apple silicon and another Mac - Apple Support

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Answer 2

Tesserax

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157,902 points

Jul 20, 2024 5:10 PM in response to MiniMum97

It would help if you can let us know what exactly you are trying to accomplish?

I'm assuming that you are referring to this Apple adapter ... correct?

Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter - Apple

If so, what Apple is telling you is that you can use this adapter two different ways:

To connect a Thunderbolt 3 device (that uses a USB-C type port) to a Mac that is only equipped with Thunderbolt/Thunderbolt 2 (DisplayPort type ports).
To connect a Thunderbolt/Thunderbolt 2 device to a Mac that only has USB-C type ports.

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Answer 3

MiniMum97 Author

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15 points

Jul 20, 2024 6:02 PM in response to Tesserax

Ok I get number two, how can you do number one when there’s no thunderbolt 2 connector (only a port)?

I want to connect a thunderbolt 3 device to the thunderbolt 2 MacBook. How can it connect to the thunderbolt 2 port on the MacBook?

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Answer 4

Tesserax

Level 10

157,902 points

Jul 20, 2024 7:15 PM in response to MiniMum97

MiniMum97 wrote:

I want to connect a thunderbolt 3 device to the thunderbolt 2 MacBook. How can it connect to the thunderbolt 2 port on the MacBook?

Then this adapter will not work, as is. You will need an adapter that has a male Thunderbolt 2 connector on one end, and either a male or female USB-C connector on the other end (depending on the device you are trying to connect to your Mac.)

You do understand that you will lose all the performance features of Thunderbolt 3 as, at best, you would only get Thunderbolt 2 throughput at that Mac's port.

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Answer 5

MiniMum97 Author

Level 1

15 points

Jul 20, 2024 8:03 PM in response to Tesserax

I’m trying to connect a thunderbolt 2 MacBook to a thunderbolt 3 MacBook so I can use the thunderbolt 2 MacBook as a drive. I understand this can only be done with a thunderbolt cable connection (not usb c).

The adapter says its “bidirectional” and that “you can use it to connect thunderbolt 3 devices to a Mac that has a thunderbolt or thunderbolt 2 port” but there doesn’t seem to be anyway to connect it so not sure what it means by this?

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Answer 6

MiniMum97 Author

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Jul 21, 2024 6:24 PM in response to Tesserax

Hi Sorry for delay in coming back to you I have been out all day today! Yes I am looking at using Target Disk Mode to use the old Thunderbolt 2 (T2) MacBook as a drive - this MacBook is a MacBook Pro Early 2015 - It has Thunderbolt 1 or 2 and USB-A as you say. I have access to both a MacBook Air 2019, and I have ordered a MacBook Air M3 which is arriving tomorrow, and these have USB-C/Thunderbolt 3/4 ports. I just need to know how to connect them as the adapter doesn't seem to have the correct connectors.

Many thanks.

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Answer 7

Tesserax

Level 10

157,902 points

Jul 22, 2024 10:15 AM in response to MiniMum97

Then you will have two choices of cables to use:

USB-A (male) to USB-C (male)
Mini DisplayPort (Male) to USB-C (Male)

The first one should be relatively easy to find. Something like this one: https://www.cablestogo.com/adapters-docks-and-hubs/usb/usb-c-adapter-cables/6ft-1-8m-usb-2-0-usb-c-to-usb-a-cable-m-m-black/p/cg-28871

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Answer 8

MiniMum97 Author

Level 1

15 points

Jul 22, 2024 12:57 PM in response to Tesserax

"Then you will have two choices of cables to use:

USB-A (male) to USB-C (male)
Mini DisplayPort (Male) to USB-C (Male)"

I don't think you can use these cables with the MBA 2019, as it says at the top of this page:

Transfer files between two Mac computers using target disk mode – Apple Support (UK)

That "If either of the computers has macOS 11 or later installed, you must connect the two computers using a Thunderbolt cable."

Hence why I was asking about the thunderbolt adapter.

It doesn't seem to say this on this page:

Transfer files between a Mac with Apple silicon and another Mac – Apple Support (UK)

So I might be able to get it to work (I have a USB A to USB C cable) on the MBA M3 I've just got when I've restored it. I've got another question open about this though so just waiting on a answer to that before I can try it......

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Answer 9

Tesserax

Level 10

157,902 points

Jul 22, 2024 1:01 PM in response to MiniMum97

If the computer you want to transfer files to is a M-series Mac, the second Support article would apply. The very first step reads:

Connect the two computers using a USB, USB-C or Thunderbolt cable.

I would then assume that USB = USB-A, and why I suggested the first cable choice.

Unfortunately, I do not have either of these Macs to test for you, so you will have to either give it a try or wait until someone else chimes in that do have this combo to offer you assistance. Good luck!

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Answer 10

MiniMum97 Author

Level 1

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Jul 22, 2024 1:19 PM in response to Tesserax

OK thank you, you've been very helpful. I was just saying in my last update that I don't think what you've suggested will work for the MacBook I've been trying to use (the 2019 one), as the instructions seem to say that you need a thunderbolt cable - which led to my question about the adapter.

I do now have a silicon MB (but this only arrived today) that the USB-C to A cable might work on, but that only arrived today. I did already try this cable with the 2019 MBA, and it couldn't recognise the old MBP disk in target disk mode. This could either be because the disk is toast, or it could be be cause I need a thunderbolt cable.

Anyway, do you know the answer to my original question, which is how can I connect the apple thunderbolt adapter between my 2015 MBP and the 2019 MBA - I am coming to my own conclusion that I think I must need another cable (a thunderbolt 2 cable) otherwise I can't see how it could possibly work.. It would be most helpful if the apple website actually said that! Saying it's bidirectional, implies to me that it should just work in both directions way without anything additional. Cables are an absolute minefield, so it would help if things like this were explained in clear and comprehensive detail!

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How is the Apple Thunderbolt 2 to 3 adapter bidirectional?

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