Sorry to break the news, but @Helios is absolutely right. Only if a device is standard USB or USB-C will it work on a standard USB-C port. This is one reason why you cannot plug in an eGPU box into a standard USB-C port. A Thunderbolt 3 port happen to fully comply with USB-C but this is because Thunderbolt 3 is Intel's proprietary extension or derivative of the USB-C standard. Said differently, a Thunderbolt 3 port is fully backwards compatible with USB-C, but USB and USB-C ports are not forwards compatible with Thunderbolt 3. Fortunately, all Thunderbolt 3 ports are compatible with Thunderbolt 2 and earlier via an adapter, and Thunderbolt 3 ports should be fully compatible (either directly or via adapters) with future Thunderbolt 4 devices. Why in Intel's infinite genius they decided to use the same port when you still have to have specialized cables and devices to even run Thunderbolt 3 is beyond me.
Plugable and other manufacturers explicitly warn about this:
Total Nightmare: USB-C and Thunderbolt 3
October 29, 2016 By Stephen
Did you buy the new MacBook or MacBook Pro? Maybe the Google Pixel? You’re about to enter a world of confusion thanks to those new “USB-C” ports. See, that simple-looking port hides a world of complexity, and the (thankful) backward-compatibility uses different kinds of cables for different tasks. Shoppers have to be very careful to buy exactly the right cable for their devices!
With Apple, Google, and many other companies jumping on USB Type-C and Thunderbolt 3, the world of connectivity just got very weird
USB Type-C: Ports vs. Protocols
USB Type-C ports have become fairly common, with Google adopting them on their Pixel and Nexus computers and phones and Apple implementing them on the 12″ MacBook and now the new MacBook Pro. This is a physical specification for a 24-pin reversible plug and associated cabling. From now on, in this article, I’m going to refer to this physical cable and port as “USB-C”, since that’s the most common usage1.
USB Type-C ports can support a variety of protocols, with each level backwards compatible to the levels beneath it
USB-C allows for a variety of signals to pass through this port:
- USB 2.0 – Astonishingly, the earliest USB-C devices, including the Nokia N1 only supported USB 2.0 signals and power delivery. Pretty much every new computer supports at least USB 3.0 speed, but some USB-C phones and tablets are similarly limited.
- USB 3.1 gen 1 – Extremely similar to “SuperSpeed” USB 3.0, this is a 5 Gbps serial connection for all sorts of peripherals to use, from hard drives to network adapters to docking stations. It’s backward-compatible with “SuperSpeed” USB 3.0, “Hi-Speed” USB 2.0, and even the original USB 1.x from way back in 1996! This is the protocol used by Apple’s 12″ MacBook.
- USB 3.1 gen 2 – This confusingly-named specification doubles the maximum throughput of USB-protocol peripherals to 10 Gbps. It’s also backward-compatible with all previous versions of USB. Only the newest USB-C devices support this high-speed protocol.2
- Alternate Mode – The physical USB-C connector can also support other non-USB protocols, including DisplayPort, MHL, HDMI, and Thunderbolt. I’ll go into more detail below, but suffice to say that not every device supports every Alternate Mode protocol, and this will be tremendously confusing for buyers!
- Power Delivery – Although not a data protocol, USB-C also allows for up to 100 Watts of power delivery to connected devices. But here again, there are two different specifications and a multitude of different configurations that will be encountered.
- Audio Accessory Mode – There’s also a spec to have analog audio use this port.
The core issue with USB-C is confusion: Not every USB-C cable, port, device, and power supply will be compatible, and there are many different combinations to consider. The newest, most full-featured devices (such as Apple’s brand-new Touch Bar MacBook Pro) will support most of the different uses for the USB-C port, but typical older devices only support basic USB 3.0 speed and (if you’re lucky) Alternate Mode DisplayPort.
And it gets worse. Many USB-C peripherals are limited in various ways as well. Consider a simple USB-C HDMI adapter: It could implement HDMI over USB 3.0 or it could use Alternate Mode (native) HDMI. It could also use HDMI “multiplexed” with Thunderbolt Alternate Mode or even (theoretically) implement HDMI over Thunderbolt using an off-board graphics chip!3 Of these options, only the newest computers, like the MacBook Pro, would support all three. Can you imagine the consumer confusion when they purchase a “USB-C HDMI adapter” only to find that it doesn’t work with their MacBook or Pixel or whatever?
These cables look identical but have vastly different capabilities. USB-C cable confusion is a nightmare waiting to happen! (I think Monoprice even re-used the same photo for two very different cables)
But the issue of incompatible cables is even more serious. Many companies, including my go-to source, Monoprice, are building USB-C cables of various quality and compatibility. If you’re not careful, you can neuter or even damage your devices by using the wrong cable. Seriously: Using the wrong cable can damage your machine! This should not be possible, but there it is.
Some cables with USB-C ports on both ends can only pass 5 Gbps data while others are compatible with 10 Gbps USB 3.1 gen 2. Other cables can’t be used for power delivery or are incompatible with Alternate Mode Thunderbolt. Check out the Monoprice 3.1 10 Gbps/100-Watt USB-C to USB-C, 3.0 5 Gbps/15 Watt USB-C to USB-C , and 2.0 480 Mbps/2.4 A USB-C to USB-C cables. Why do all these variations even exist?4
And then there are the cables with different connectors on each end: Monoprice sells an awesome USB-C to USB 3.0 10 Gbps adapter but also has one that only goes to 5 Gbps and another that’s limited to 480 Mbps USB 2.0. And they all look almost identical. What a nightmare for consumers!5
Note: I don’t mean to be picking on Monoprice here. I love their cables and just ordered over $100 of carefully-selected Monoprice USB-C cables. But their wide range of USB-C cables aptly illustrates the very real problem of incompatibility, so I’m using them as an example. Literally every vendor of USB-C cables, from Apple to Belkin to StarTech, has this same issue.
Now we turn to an even-more confusing topic: Thunderbolt 3. Mac owners, since the debut of the early-2011 MacBook Pro, have become accustomed to the Mini DisplayPort connector serving double-duty as both a graphics and data port. And they’ve also gotten used to the head-slapping experience of plugging a Thunderbolt cable into a basic Mini DisplayPort jack and finding it doesn’t work.
This same experience is repeated with USB’s new Type-C port:
- Not all USB-C device ports have the same capability – Many are data-only, some can do data and video, and a few can do data, video, and Thunderbolt 3!
- Thunderbolt 3 requires a special cable – Although it looks exactly the same as a regular USB-C cable, you need a special Thunderbolt 3 cable to use Thunderbolt 3 devices!
- Thunderbolt 3 devices look just like regular USB-C devices – Most ordinary devices with a USB-C cable are limited to 5 Gbps (or even less) of USB data but Thunderbolt 3 devices pass PCI Express data and boast 40 Gbps of throughput!
Thunderbolt 3 ports and cables ought to be backward-compatible with USB 3.1 Type-C cables, ports, and devices. But of course they will run at that slower speed and lack Thunderbolt connectivity in that case. Thank the maker for backward compatibility!6
So owners of Thunderbolt 3-capable machines like the new late-2016 MacBook Pro must be very careful when buying devices and cables to make sure they get the performance they expect. Most of Apple’s current USB-C accessories and cables will work with the new MacBook Pro (it’s backward-compatible) but might not deliver the full Thunderbolt 3 experience. And owners of the older 12″ Retina MacBook are even more at risk, since, although Thunderbolt 3 devices will plug right in, they will not function at all!7
Since Thunderbolt 3 can also include both data and video, it can be very confusing knowing whether a given computer, cable, and device are compatible. For example, a Thunderbolt 3 cable can support two 4K 60 Hz monitors or even a 5K display, while a USB-C cable is limited to just one 4K monitor.8
Sadly, Apple appears not to have included the Thunderbolt icon on the new MacBook Pro ports, creating even more customer confusion!
Note that there are both 40 Gbps and 20 Gbps Thunderbolt 3 cables. And the MacBook Pro is not compatible with the first-generation Texas Instruments Thunderbolt 3 controller used in many early Thunderbolt 3 devices. Be very careful when buying!
With this insane level of “compatibility” for the new USB Type-C port, buyers must be very careful when purchasing cables and devices. Although it’s great that the industry is moving to a simple, durable, reversible port for data, video, and power, this mix-and-match device and cable situation is bound to frustrate consumers and cause technical headaches. Buyer beware!
You should also read my 2016 MacBook Pro USB-C/Thunderbolt Survival Guide. It’s the brighter/cheerier follow-up to this post!
Addendum: If It Fits, It Should Work
This article has received a ton of attention (Hacker News will do that), with many positive and critical comments. Among the chief criticisms is that I’m being alarmist and that the real-life situation for USB-C isn’t all that bad. And today, for the most part, this is true, because these people have USB-only Nexus phones and so on. But I feel that there’s a looming issue with the proliferation of uses for this “do it all” cable/port and that this will lead to the “nightmare” of my headline. Here’s why.
Electronics are no longer the realm of the geeks. Most computers, phones, tablets, and peripherals are purchased by people who are not technically savvy. They don’t know a protocol from an interface and really shouldn’t have to be bothered learning that “USB Type-C” is different from “Thunderbolt 3” or “USB 3.1”. They want to buy stuff, plug it in, and have it work. They judge compatibility by the shape and fit of the connector, not the specs or logos on the package.
Historically, the industry has done a pretty good job of this. After some initial teething issues, USB has become a real boon for average device users. Cables, devices, and peripherals all pretty much work. Although the experience of USB 3, Mini USB, Micro USB, and high-power chargers hasn’t been all that positive, the consumer expectation that “if it fits, it works” still holds true for the USB of today. Heck, I’m using a cheap swag USB cable right now! The core reason for this is that USB has always been both a cable and a protocol. Apart from power delivery (how many iPads are slowly charging on iPhone cubes?) USB has worked because USB is USB.
Now along comes a “do it all” cable that can literally be the only port on a device. Data, video, and power all share the same USB Type-C port. And Intel just kicked it into high-gear by adding a totally separate world of data and video support called Thunderbolt 3. It’s not realistic to expect that every port, cable, and device will work properly together, especially when it’s so much cheaper to build a basic USB 3.1 gen 1 or even USB 2.0 cable or device.
Starting now (since Thunderbolt 3 devices are shipping) we have a port that defies consumer expectations: Cables will not be compatible and devices will not support certain peripherals even though the port looks the same. This is the nightmare scenario: Consumers will pull “the wrong cable” from the drawer, store, or bag and will assume a peripheral or charger is broken when it doesn’t work. We’ll see frustration, returns, and misguided tech support proliferate.
This is the age-old push and pull of compatibility. We enhance compatibility only to raise consumer expectations that everything will just work. USB Type-C will never just work because USB-C is too many different things at once. This is the nightmare.
- Google tells me that this port is called “USB-C” 21 million times, “USB C” 12 million times, and correctly “USB Type-C” only 8.5 million times. Majority rules: “USB-C” wins.
- Talk about a name designed by a committee! Who thought “USB 3.1 gen 2” was a good thing to call this?
- I’m the guy who popularized the idea of an Apple Thunderbolt Display with an integrated GPU.
- Why make a 2.0-only USB-C to USB-C cable? I guess it’s intended for a bone-headed device like that old Nokia N1, but at this point this useless/incompatible/worthless cable should probably cease to be sold…
- Note that Monoprice incorrectly names every 5 Gbps cable “USB 3.0” and every 10 Gbps cable “USB 3.1”. Although it’s wrong, I think this naming is much more consumer-friendly than the official terms.
- Note that this is a simplification: Thunderbolt 3 is really an “Alternate Mode” use of the Type-C port/cable, just like HDMI. But in practice, Thunderbolt 3 is a super-set of USB 3.1 for USB-C since no implementation of Thunderbolt 3 will be USB 2.0 only.
- Apple has been pretty good about calling all non-Thunderbolt ports and cables “USB-C” and adding “Thunderbolt 3” where that protocol is supported. but it’s unconscionable that they’re no longer labeling the ports with some kind of icon!
- Funny enough, USB-C Alternate Mode has different video compatibility than Thunderbolt 3: While Thunderbolt 3 supports HDMI 2.0, USB 3.1 can only do HDMI 1.4b. But when it comes to DisplayPort, USB 3.1 has the upper hand, supporting version 1.3 vs. version 1.2 in Thunderbolt 3. Support for these protocol levels is entirely dependent on the implementation of the port in a given machine.