When Thunderbolt 3 arrived, it was touted as not only twice as fast as previous generations, but completely backwards compatible with Thunderbolt 1 and 2. Signal-wise, that’s perfectly true. Physically, err... Thunderbolt 3 ditched the previous generation’s mini-DisplayPort connector for the slimmer, trimmer, orientation-agnostic USB Type-C port.
That was a nice move actually, but while adapters for the still plentiful Thunderbolt 2 Macs and perhipherals arrived in short order, they didn’t support bus-power-only devices like all those sexy Thunderbolt portable SSDs I review for Macworld. Bummer.
However, there’s always been an easy, albeit somewhat pricey and not particularly portable solution: a powered dock.
Uni-directional and powerless adapters
One of the cross-generational adapter designs that came out with the arrival of Thunderbolt 3 was apparently designed under the assumption that users would only want to connect their older Thunderbolt 2 devices to their new Thunderbolt 3 Mac. Said presumptuous (penny-pinching?) design, was fine for that, but was generationally uni-directional, not allowing you to hook up Thunderbolt 3 devices to Thunderbolt 1/2 Macs. Oops. Avoid these.
Thankfully Apple realized that users of older Macs might want to make use of newer Thunderbolt 3 devices and made their adapter bi-directional version-wise. Shown above, the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter ($49) is the one you want. Great! Almost.
For some reason, none of the adapters—including Apple’s—deliver bus power to devices. The upshot being that any Thunderbolt device that provides its own power works with the adapter, while bus-power-only (no AC adapter) devices such as the aforementioned portable SSDs, audio interfaces, etc. will not.
Most articles I’ve seen online (unfortunately some of them mine) have intimated or flat out said this is simply the way things are, ignoring the easy if not particularly cheap solution.
Sitting in a dock is okay
The answer is of course, a powered Thunderbolt dock sitting on the end of the Apple adapter. Said dock needs to match the version of Thunderbolt (1/2 or 3) you want to use, but don’t have. That is, to attach bus-powered T3 devices to a T1/2 Mac, you need a T3 dock. To attach bus-powered T1/2 devices to a T3 Mac, you need a T1/2 dock.
Two criteria must be met in either case: the dock must have its own power supply, and it must have two Thunderbolt ports. The first port is for the computer, and quite often labeled as such, with of course the Apple adapter and a cable placed between the computer and the dock. The second is to connect the downstream device, which is the whole point of the exercise. You would think all powered docks would have two ports, but check to make sure.
Powered Thunderbolt 3 docks were running anywhere from $175 to $250 on Amazon and around the same on eBay when I went shopping. Powered Thunderbolt 2 docks were scarce as hen’s teeth on Amazon, but there were quite a few on eBay and some vendor sites.
Note that you’ll see portable, or mini-docks advertised at prices that may catch your eye. All of those that attracted my ocular orbs relied on bus power for their own needs and those of attached devices. These won’t do.
Theory meets fact
Using the Apple adapter and a powered Thunderbolt 1/2/3 dock should work with just about any Thunderbolt device, but of course testing was in order before recommending that you, dear reader, fork over several hundred smackaroos. If you’re wondering why I hadn’t previously... I never had the need, and from talking to vendors, not a lot of them had felt compelled either. It was really my interest in Universal Audio’s Arrow Thunderbolt 3 audio interface, which runs only on bus power that piqued my curiosity.
Long story short, I tested a number of Thunderbolt 3 devices on a CalDigit TS3 Thunderbolt 3 dock connected to a Thunderbolt 2 iMac via the Apple adapter and they all worked. Of course, as Thunderbolt always drops to the lowest data rate in a chain, they operated at Thunderbolt 2 speeds, but the fact that they worked at all was okay in my book. I also tried several Thunderbolt 2 drives using Belkin’s F4U055 Thunderbolt 2 dock attached to a Thunderbolt 3 Macbook Pro with the same 100 percent success rate.
Not having a Universal Audio Thunderbolt 3 interface at the time of this writing, I’ll rely on the assurance from one of their reps that it works perfectly. It should. All the current Thunderbolt chips are from Intel, and they’ve done a bang up job of maintaining compatibility across generations and with the technology in general. Apple did a bang up job on the company’s adapter. I don’t expect to hear of any problems for you guys, but by all means let me know if you run into any.
Pricey but worth it
I, like many of you I’m sure, don’t need or want to buy a new Mac. My older 2015, 5K 27-inch iMac, especially after upgrading the storage is just fine by me. Better than fine actually. You might also be rocking a newer Mac and simply want to leverage an older bus-powered drive.
In either case, you can have your Thunderbolt cake and eat it too—as long as you’re ready to pony up $175 to $300 for the adapter and dock. You also get more ports in a handier location, so what’s not to love? Okay, laptop users might not be crazy about dragging around another device. C’est la vie.
Note that Thunderbolt 4 is right around the corner, but will continue to use the same Type-C connector so this solution should be forward compatible.