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I have a Thunderbolt 3 device that is a 1080p LCD monitor. When the device is connected, System Profiler lists its monitor as using a DisplayPort connection, as well as a few USB 2 devices since this device has touch screen capabilities. It has no external power source -- it's typically powered over its Thunderbolt 3 connection when connected to an actual Thunderbolt 3 port.

I'm wondering if it's possible for me to connect this device to a Mac with a Thunderbolt 2 port and use it as a monitor? In theory this is possible since Thunderbolt 2 supports DisplayPort and could provide more than enough bandwidth and power for a 1080p LCD monitor. It would be nice if this device's USB 2 capabilities worked as well, but not a big deal if they don't. Basically, I'm not sure any such adapter exists for this sort of thing, or if it would work for my particular needs.

Is this possible? For example, can I use the Apple Thunderbolt 2 to Thunderbolt 3 adapter + a male-to-male Thunderbolt 2 cable to accomplish this? Or maybe just a male-to-male Mini DisplayPort cable?

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  • What is the make and model of this Thunderbolt 3 display?
    – drivec
    Dec 8, 2017 at 18:40
  • Unfortunately it's a prototype / testing device so I can't give any specific information about it.
    – Bri Bri
    Dec 8, 2017 at 19:16
  • "System Profiler lists its monitor as using a DisplayPort connection, as well as a few USB 2 devices" - this sounds more like USB-C alt mode rather than TB3.
    – Agent_L
    Mar 28, 2023 at 9:08

2 Answers 2

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No, that is not possible. Thunderbolt 3 is required to support the power delivery (USB-PD) over the Thunderbolt cable.

As your display has no external power source, it won't help that you get the display signal to it, as it would have no power.

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  • Doesn't Thunderbolt 2 support delivering power?
    – Bri Bri
    Dec 9, 2017 at 13:52
  • You sure about that? For example: apple.stackexchange.com/questions/124485/…
    – Bri Bri
    Dec 9, 2017 at 14:47
  • Well, I was talking about power for a PC monitor. The Thunderbolt standard does allow for supplying power very much similar to traditional USB ports. It is on the order of 10W - suitable for charging a smartphone for example. It is not nearly enough to power an ordinary PC monitor. With Thunderbolt 3 and USB-PD you can supply up to 100W, which is the sort of power required for a full monitor. So no, unless you’re talking about a very small monitor (i.e. a 5” monitor for example), you’re not going to be able to power it over TB2.
    – jksoegaard
    Dec 9, 2017 at 16:19
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I realize the question is old but it seems to be getting bumped up lately so apparently there is still some interest.

Is this possible? For example, can I use the Apple Thunderbolt 2 to Thunderbolt 3 adapter + a male-to-male Thunderbolt 2 cable to accomplish this? Or maybe just a male-to-male Mini DisplayPort cable?

A TB2-to-TB3 adapter should work if the display is truly a Thunderbolt display. I found out with some digging into the specs that while DisplayPort and Thunderbolt might use the same connector the cables are wired differently. Thunderbolt cables are wired in a crossover, while DisplayPort is wired straight through. Even if someone picks the right cables there may be differences in how the communication is done that prevents something from working.

The mini-DP port used on older versions of Thunderbolt will support only 10 watts, and even then I'm not sure if the spec allows that power to be transferred to any devices, that power might only be for adapters and active cables. What might work is having a Thunderbolt hub or dock with USB-C ports that will supply power. The connection to the hub or dock can be through a TB2-to-TB3 adapter, then the hub provides power and the USB controller for the display. All Thunderbolt/USB-C hubs are required to have USB controllers for backward compatibility. Not all USB-C cables will support passing through the USB protocol. This might sound odd that USB cables aren't required to carry USB signals but that's what happens when piling new on top of old.

Then again this question is a bit old so people looking for answers to anything like this may be few. Perhaps helpful for people looking to operate older hardware with newer hardware attached.

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