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Apple released Thunderbolt 3 to Thunderbolt 2 adapter. Is it possible to connect an external device using type C (ie ASUS MB169B+) by connecting the Thunderbolt 3 to Thunderbolt 2 adapter with an Thunderbolt cable into the Mac (this is an older Mac before 2015)?

Can the MacBook (which only supports Thunderbolt 2) fully access the device which supports type C? The transmission traffic still won't compare with the real Thunderbolt 3 speeds but at least the Thunderbolt 2 ports are not useless!

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Lets break your question into two questions. The first question is "Can I use the ASUS MB169B+ with a Thunderbolt 1/2 Mac?" The second question is "Is there a generic way to connect any arbitrary Thunderbolt 3 or USB Type C peripheral to a Thunderbolt 1/2 Mac?"

First let me address your specific example. The ASUS MB169B+ is actually just a regular USB 3.0 device. It uses a technology called DisplayLink which basically is a video card connected over USB (instead of the typical PCIe connection.)

Because MB169B+ is a regular USB device, you can simply connect it to one of your MacBook's regular USB ports and it will work just as well as it would connected to a USB Type C port.

Now for the second question, can you use a Thunderbolt 3 (or USB Type C) peripheral with a Thunderbolt 2 computer? Theoretically, yes it is possible to create a dongle that accomplishes this. You would have to put a Falcon Ridge controller and an Alpine Ridge controller in to the same dongle and connect them together like so:

            +--------Thunderbolt 2 to 3 Adapter Box--------+
            |                +--> PCIe --+                 |
MacBook --> | Falcon Ridge --|           |--> Alpine Ridge | --> Thunderbolt 3/Type C
            |                +--> DP ----+                 |
            +----------------------------------------------+

While a dongle exactly as above does not exist, there is an interesting workaround. The Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter you mention has some limited ability here. While the Apple adapter does work as a generic 3 to 2 adapter, it can only go from 2 to 3 if the peripheral on the other side is a native Thunderbolt 3 device. For example, this adapter works for connecting a LG UltraFine 5K Display to a Thunderbolt 2 Mac. However, it won't work with the 2016 21.5" LG UltraFine 4K Display since that monitor is USB-C only and not a Thunderbolt 3 device. It will work with the 2019 23.5" LG UltraFine 4K Display since that monitor has Thunderbolt 3.

Now, here is where things start to get weird. If you buy a Thunderbolt 3 dock, for example the CalDigit TS3 Plus Dock you can use the Apple adapter to connect a Thunderbolt 2 Mac to it. Most Thunderbolt docks have two Thunderbolt ports on them, one upstream port to connect the computer to the dock and one downstream port for daisy chaining more Thunderbolt devices. That downstream port is actually a full featured USB-C port as well, with support for Thunderbolt 3, Display Port Alternate mode, and USB 3.1. So you can actually plug the 2016 21.5" LG UltraFine 4K Display in to that downstream port and it will work!

Its pretty crazy but the following connection sequence actually works:

Thunderbolt 2 Mac --> Thunderbolt 3 to 2 Adapter --> Thunderbolt 3 Dock --> 2016 21.5" LG 4K

But this sequence (un-intuitively) does NOT work:

Thunderbolt 2 Mac --> Thunderbolt 3 to 2 Adapter --> 2016 21.5" LG 4K

So in summary, the combination of the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter with a Thunderbolt 3 dock creates a fully featured (and expensive) Thunderbolt 2 to Thunderbolt 3 adapter.

UPDATE:

It appears that at some point one of the newer patches to macOS High Sierra has tweaks to its Thunderbolt driver stack that makes the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter function pretty well as both a 3 to 2 adapter AND a 2 to 3 adapter. The original version of this post mentioned that it did not work, that information is now out of date and I have updated the post accordingly.

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    We are now mid-2018. Has anything evolved on this front? In my case, I would like to connect Macs with Thunderbolt ports to an LG UltraFine 4K Display. – Jean-François Beauchamp Jun 19 '18 at 23:17
  • I want to connect my late 2015 macbook to my z390 desktop. when I have powerful graphics desktop with thunderbolt 3, why do i need an eGPU for my macbook? – Necktwi Aug 29 '19 at 4:45
  • and you saved me from buying the marketed adapter. – Necktwi Aug 29 '19 at 5:13
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    @nateman1352 Thanks for the answer. This might be a dumb question but how do I connect a Thunderbolt 2 Mac to the Thunderbolt 3 to 2 Adapter? Don't they both have a female Thunderbolt 2 connector? – Domon Mar 17 at 6:45
  • @domon you basically plug the adapter in backwards: you plug the male (TB3) end into the dock and the TB2 end then can be connected to the computer via an additional TB2 male to TB2 male cable. It works great with the aforementioned CalDigit dock and mostly well with the CalDigit USB-C Pro Dock. Alas, it doesn't work with any dock that has an integrated cable, since I haven't found a way to couple a TB3 male cable to the adapter's TB3 male end. – Timothy R. Butler Aug 7 at 3:40
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All Mac with thunderbolt 2 are limited since thunderbolt 2 doesn't embed USB C. Even with the thunderbolt 2 to thunderbolt 3 adapter, you could physically connect a USB C display like the ASUS MB169B or the LG 4K Display and they won't work.

New Mac with USB C connectors will work and don't need the adapter. whether you have the MacBook "one" or the MacBook Pro that combine thunderbolt 3 and USB C in one physical port, they should connect to USB C displays.

The only case where a thunderbolt 2 Mac can drive a new connector display with the adapter is if the display supports thunderbolt explicitly as opposed to USB. The LG 5k display is one such new monitor that would work with many thunderbolt 2 Mac. This results in lower resolution, though - 3840 x 2160 @ 60Hz

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You can do this with a simpler and cheaper USB-C female to USB-A male adapter. For example you could buy this:

https://www.amazon.com/Lemeng-USB3-0-Connector-Converter-Adapter/dp/B01ABTHI7C

Note that this only works with USB devices, i.e. for example monitors that need the alternate-mode DisplayPort signal won't work.

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IN reality the older TB2 mac may lack the proper video output rendering a 2K output. If one has the Retina which support 4k then that unit has HDMI onboard or one has a Mac Pro Tower and then a high end video card is in line with a possible solution. In any case I do not believe the TB2 can push the speed necessary for 4K or greater.

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See the below apple product Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter

The Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter lets you connect Thunderbolt and Thunderbolt 2 devices — such as external hard drives and Thunderbolt docks — to any of the Thunderbolt 3 (USB-C) ports on your MacBook Pro. As a bidirectional adapter, it can also connect new Thunderbolt 3 devices to a Mac with a Thunderbolt or Thunderbolt 2 port and macOS Sierra.

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  • This is not necessarily true. As pointed out above the adapter does not give the older Thunderbolt 2 computer the embedded USB C protocols that it lacks. A T3 peripheral that happens to have a USB C port would theoretically work but really it would probably have an actual T3 port not a USB-C. And T3 is backwards compatible with T2 at T2 speeds/protocols. – Beartech Dec 22 '17 at 18:01
  • Also as I discovered, the Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter does not pass power. I wanted to use it to connect a bus powered Thunderbolt 3 SSD drive to my older iMac until I can upgrade it. Turns out this seems to be impossible. – Robert J Berger Mar 23 '19 at 19:08
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I have the following setup and it does work:

Power is not passed though. USB 2.0 is passed through (tested Epson V550 scanner with a USB 2.0 to USB-C adapter). I have not tested USB 3.0 passthrough.

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Well ASUS MB169B+ support page has a download for MacOS 10.15.5 or greater. So it seems it will in fact work. Since this was an old question, it might not have worked 3 years and 3 months ago.

The ASUS website doesn't like Safari try Chrome/Firefox instead: https://www.asus.com/us/Monitors/MB169BPlus/HelpDesk_Download/

Version 1.0.0 2020/07/1710.28 MBytes

MB Series USB Monitor APP for Mac OS 10.15.5 or higher This APP enables you to use ASUS MB series monitor with Mac OS system via USB 3.0 signal. If your operation system is upgraded to Mac OS 10.15.5 or higher, please upgrade and install this APP accordingly. If your operation system is still staying at version before Mac OS 10.15.5, please keep using driver 5.2.1 version When connecting with USB 3.0 mode, certain content or apps with security protection on host devices may prohibit the viewing of protected content on MB series monitor. If you have paid media content on your device, it is possible your app may limit its viewing to your host device only.

ASUS makes mention of earlier drivers but doesn't provide anything prior to Mojave on their web page. But apparently those drivers/apps were available in the past.

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