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How can I connect an external USB-C/Thunderbolt 3 device to a Thunderbolt 2 port on my MacBook Pro?

How can I connect an external USB-C/Thunderbolt 3 (TBT3) compatible device (an external portable drive TBT4/TBT3 USB-C) to a Thunderbolt 2 port on my MacBook Pro 13" Retina (late 2013) laptop?


I tried two different Apple TBT3 (USB-C) to TBT2 adapter cables on the USB-C external device/drive end then connected a TBT2 cable into the adapter going to TBT2 on the computer end, yet can't get it to work. {Tried with two TBT3 to 2 Adapter cables, 2 different TBT2 cables and 2 different TBT2 ports on the MacBook}.


The USB-C to USB-A cable works connected to USB 3 Type A (USB-A) port on the computer, though I want to use Thunderbolt 2 port on the computer, for speedier transfers. Will this work with TBT2, and if so, how?


Earlier Mac models

Posted on Jun 13, 2023 8:30 PM

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Jun 13, 2023 8:58 PM in response to dc26

dc26 Said:

"How can I connect an external USB-C/Thunderbolt 3 device to a Thunderbolt 2 port on my MacBook Pro?"

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Troubleshooting Connectivity:


Reset the SMC and your NVRAM:

(Applies to Intel-Based Macs Only) Sometimes when changes are made to the system(i.e. updates), system configurations (i.e. for ports) become manipulated, technically. So, reset the SMC and NVRAM. It may take up to three tries. So, be certain you have time your hands while doing so.


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Jun 14, 2023 3:50 PM in response to dc26

A lot of descriptions on Amazon are confusing when it comes to USB-C, Thunderbolt 3, and Thunderbolt 4. Here is the deal:


  • Thunderbolt 3 and 4 are optional features for USB-C and USB4 host ports.
  • By definition, any Thunderbolt 3 or 4 port is also a USB-C port.
  • The converse is not true. You can have USB-C without Thunderbolt (like the 12" Retina MacBooks do).
  • At least in Apple's implementations, any USB-C port equipped with Thunderbolt 3 or 4 ALT mode also has support for USB data transfer (some flavors), USB power delivery, and DisplayPort ALT mode.
  • Therefore, Apple and others often emphasize the Thunderbolt 3 or Thunderbolt 4 – the thing that in their mind, distinguishes the ports from plain USB-C (USB) or USB-C (USB, DIsplayPort ALT mode) ports.
  • This doesn't mean that everything is going to use Thunderbolt. It's emphasizing the "highest" feature.
  • Accessory makers want to emphasize that their products will work with Macs that have Thunderbolt ports. After all, Apple emphasizes "Thunderbolt" in their marketing, and many customers aren't completely clear about the distinction between Thunderbolt and USB-C.
  • Neither are many of these third-party vendors, and in their product descriptions, they often - and usually accidentally - blur the line between a "Thunderbolt-compatible-device" (that doesn't use Thunderbolt 3, that's really a "plain" USB-C device, but that works on Thunderbolt 3 ports because Thunderbolt 3 implies USB-C) and a device that uses – and relies upon – Thunderbolt for its operation.
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Jun 13, 2023 9:23 PM in response to kaz-k

Hi,


Q to the Littles:

Should I have the drive connected when I reset the SMC and NVRAM?


Will give it a try though am thinking I should have the drive attached when re-setting these so the computer sees the device during the re-sets. I could also try both, with drive attached and if that doesn't work, then without the drive attached, if needed.


To kaz-k:

Yes, the two adapters I am using are official Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter cables.


Thanks for the suggestions.

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Jun 14, 2023 6:09 AM in response to dc26

what model-year Mac and what screen size?


what external enclosure/device or a link to its specs?


Rotating Magnetic drives or SSD drives, and how inherently fast are the drives? and are you also applying striped RAID?


what test results are you obtaining with just USB adapters?

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Jun 14, 2023 7:25 AM in response to kaz-k

Note that the Apple Thunderbolt 3 to Thunderbolt 2 Adapter is only for connecting two Thunderbolt devices.


If you connect the Thunderbolt 2 side to an older Mac, the only thing that will come out of the Thunderbolt 3 (USB-C) side is Thunderbolt. Not USB. Not DisplayPort Alt Mode. So you can't use the adapter to hook up "plain" USB-C hubs, USB-A adapters, USB-C displays, and USB-C display adapters. It will not offer the USB, DisplayPort Alt Mode, and/or USB Power Delivery services they might be looking for.


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Jun 14, 2023 11:51 AM in response to dc26

That appears to be a USB-C enclosure - not a Thunderbolt one. The references to Thunderbolt are a little bit on the confusing side (as with many Amazon product listings), but I think they are just trying to reassure customers that it will work on a computer with a USB-C "Swiss Army Knife" port advertised as a Thunderbolt 3 port.


If you plug it into a Thunderbolt 3 or 4 port on a Mac, it'll work, because all of those ports also support USB data transfer of one type or another. If you plug the TB3 end of the Apple TB3-to-TB2 adapter into it, it won't work – because the adapter will be providing a USB-C ( TB3 ) connection and the enclosure wants a USB-C ( USB) one.

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Jun 14, 2023 11:59 AM in response to dc26

RE: "The USB-C to USB-A cable works connected to USB 3 Type A (USB-A) port on the computer, though I want to use Thunderbolt 2 port on the computer, for speedier transfers. Will this work with TBT2, and if so, how?"


Thunderbolt extends PCIe-type expansion "outside the box." A Thunderbolt dock could theoretically add USB 3.1 Gen 2 ports to your Mac much like a PCIe expansion card would add them to a Windows PC. Then if you plugged the enclosure into one of the USB ports on the dock, you could get the extra speed.


However, I don't know how many docks you're going to find with this feature, and the cost of adding a dock just to get USB 3.1 Gen 2 for one device may make this impractical.

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Jun 14, 2023 1:19 PM in response to Servant of Cats

Yes, very confusing--since product descriootion states it is compatible with TBT3 I thought a TBT3 to 2 adapter would work. I believe Cable Matters USB-C does NOT work with Thunderbolt.


No power with the USB-C/TBT3-TBT2 Adapter cable, get power and enclosure/drive works with a USB-C to USB-A cable, though I want the Thunderbolt SPEED.


I believe the drive enclosure is not compatible with Thunderbolt 3 / 2 (I e-mailed the company and suggested they edit the description as it states it's compatible with TBT3, but that might reduce sales so not sure they will.


It is very confusing whether USB-C and TBT3/2 ports WILL OR WON"T work together, yet companies advertise items as working with TBT3. For example, OWC even sells a USB-C/TBT enclosure with or w/o a drive and INLCUDES an Apple TBT3 to TBT2 adapter, so I wonder IF OR HOW their USB-C enclosure works with Thunderbolt??


Makes me wonder: Do some USB-C cables provide power to work with Thunderbolt / Thunderbolt Adapters?

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Jun 14, 2023 1:25 PM in response to dc26

The ThunderBolt-3 <-> Thunderbolt-2 adapter does not provide power across the interface.

USB cables do. Thunderbolt cables also do, and can be used as an expensive replacement for USB cables.


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What test results are you obtaining with just USB adapters? (if you don't already have a drive speed test Black Magic Disk Speed Tester is free and easy to use.)


Rotating Magnetic drives or SSD drives, and how inherently fast are the drives?



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Jun 14, 2023 1:26 PM in response to Servant of Cats

Using just an HDD as an independent drive in this enclosure. I don't believe this enclosure supports TB3 even though title and product description say it is compatible with TBT3.


The USB-C included does not provide the power needed to support devices (like Thunderbolt and USB 3-Type A ports do) and this enclosure does not have a power port or different type of cable to provide power.

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Jun 14, 2023 1:34 PM in response to Servant of Cats

Yes, I was considering getting a dock because many devices are now USB-C though Thunderbolt 2 docks are very EXPENSIVE. And so far I only have this one USB-C device. Will have to consider the dock more...


At this point, I have several internal 2.5 and 3.5 inch drives that I am trying to get into enclosures to be able to access data and use them. I upgraded two macs and last week had BOTH my Thunderbolt 2 drives in external enclosures die (a G-Tech GDrive 4TB and a Lacie d2 4TB, my two largest drives).


What a couple of weeks it has been.

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Jun 14, 2023 1:43 PM in response to dc26

Ok, that takes a SATA internal drive.


Solid State Drives SATA SSD drives you could install in it can attain maximum nominal 6,000 Mega bits/sec or about 550 M Bytes/sec speeds, about 10 times faster than the fastest Rotating Magnetic drives. 


Your USB ports are two USB 3.0 ports. They can run at a top speed of 5,000 Mega bits/sec, or roughly 500 MegaBytes/sec.


Unless you need the maximum speed of the absolute fastest SATA SSD available, you Already WON!

Just use a simple USB adapter. No stinking ThunderBolt is required!

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How can I connect an external USB-C/Thunderbolt 3 device to a Thunderbolt 2 port on my MacBook Pro?

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