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Explaining Thunderbolt 3, USB-C, and Everything In Between

The first Mac with Thunderbolt 3 is now available, the non-Touch Bar 13-inch model from Apple’s new series of MacBook Pro laptops (see “New MacBook Pros Add Context-sensitive Touch Bar,” 27 October 2016); the rest of the models ship soon. Thunderbolt 3 relies on the USB-C physical connector and, with the appropriate adapters, supports nearly all common peripheral-connection and networking protocols, including USB 2, USB 3, FireWire, Thunderbolt 2, Ethernet, and DisplayPort, and by extension, HDMI, DVI, and VGA.

The reason confusion afflicts this space is that a USB-C port on another computer may support just USB, USB plus display and networking protocols, or all of that plus Thunderbolt 3. The 12-inch MacBook’s USB-C port, for instance, natively supports USB 2 and USB 3 along with DisplayPort and, via adapters, VGA, HDMI, and Ethernet connections, but not Thunderbolt 2 or FireWire.

The summary for potential late 2016 MacBook Pro owners is that all current USB-C devices, cables, and adapters should work when plugged into a MacBook Pro’s Thunderbolt 3 ports. However, Thunderbolt 3-specific devices won’t work with computers and other devices like the 12-inch MacBook whose USB-C ports are less capable. Now, let’s drill down into details.

How These Standards Relate to Each Other -- USB-C is a standard developed by the USB Implementors Forum to modernize and coalesce USB into a single plug style that supports a variety of data, video, and power options for ports, cables, and adapters. It’s reversible, just like the Lightning plug Apple uses for iOS devices and recent peripherals like the Apple Pencil and Magic Mouse 2.

Support for high-wattage and high-amperage cables allows USB-C chargers to charge laptops and other devices. While previous versions of USB allowed for high power flow, USB-C is the first version in which laptops take advantage of that, allowing external charging from an AC adapter or external battery. USB-C also offers bidirectional power, so a MacBook Pro could recharge itself via an external battery while also charging an iPhone.

(Although we’re focusing here on USB-C, or more formally, USB Type-C, USB also supports other plug types. These include USB Type-A, the standard rectangular USB plug we’re all accustomed to; USB Type-B, the squarish USB plug often used by large peripherals; and the smaller Mini-A, Mini-B, Micro-A, Micro-B, and Micro-B SuperSpeed plugs.)

USB-C appeared first in 2015 in the 12-inch MacBook, and shortly thereafter in equipment from Google and others. It has spread gradually, but it is still not the connection of choice for laptops and mobile phones. The third-party peripheral market, especially for docks and high-quality cables, started to accelerate only in early 2016.

Thunderbolt 1 and 2 use the same physical connector as Mini DisplayPort, which allowed a jack to fit easily into a thin laptop. Natively, they support two protocols: Thunderbolt (originally built on top of PCI Express) for general data and DisplayPort for video. With adapters, they can also carry USB, FireWire, and Ethernet.

Although Intel developed Thunderbolt jointly with Apple, Intel seems to control its future. In June 2015, Intel and the USB Implementors Forum announced that Thunderbolt 3 would rely on the USB-C plug style. That was good news: one fewer cable type and all ports would become multi-purpose! How this works has to do with abstraction: the hardware no longer defines a single associated communications protocol.

USB-C and DisplayPort exist both as a physical specification for connectors and cables, and also as a logical protocol that defines how data moves across a data bus. The USB-C data bus has a number of channels (called “lanes”) that can be assigned and configured to different protocols, depending on the USB-C controller hardware in the host computer or other device, including USB, DisplayPort, PCI Express, and Thunderbolt. DisplayPort can either use its own connector type or be encapsulated and carried by other standards, which include USB-C, whether or not the controller hardware supports Thunderbolt. This capability of DisplayPort made it possible for Thunderbolt to use the Mini DisplayPort connector type and be backward compatible with existing DisplayPort devices.

Thunderbolt allows daisy chaining — plugging one peripheral into the next — though DisplayPort monitors have to be at the end of such a chain. Though I can’t find a definitive answer, it appears that you cannot daisy chain USB devices connected via USB-C, although you can simulate daisy chaining with the addition of USB-C–connected hubs. Power, which is effectively a different kind of protocol in USB-C, can be passed through multiple devices.

When it comes to protocols, USB-C natively supports:

  • USB 2.0 (480 Mbps)

  • USB 3.0 (5 Gbps, branded SuperSpeed, now described as USB 3.1 Gen 1)

  • USB 3.1 Gen 2 (10 Gbps, branded SuperSpeed+, which requires USB-C as a connector type)

  • DisplayPort (under the ungainly name “DisplayPort Alternate Mode on USB Type-C Connector Standard”)

  • MHL 3.0 (Mobile High-Definition Link, which you’ve probably never heard of: it’s a way to connect mobile devices to HD displays)

  • Thunderbolt 3 (on computers that have Thunderbolt 3 controllers, like the new MacBook Pros)

USB-C can create the appropriate electrical signals for these natively supported standards internally and pass them through a cable with a USB-C plug on one end and the native format, like DisplayPort or USB 3 Type-A, on the other. Some of these are in the form of a dongle with a jack on the non-USB-C end, but it’s still sending the signal straight through.

For other protocols, you need an adapter, which performs internal signal conversion between USB-C and the adapter’s input port, like HDMI, VGA, Ethernet, and FireWire. (The HDMI trade group added USB-C as an option recently and says that monitors with native USB-C support will be out in 2017. For now, Ethernet is supported directly only in a 10 Gbps peer-to-peer version that’s part of Thunderbolt 3.)

USB-C can drive at least a single 4K monitor, depending on the display circuitry on the host device. A computer with Multi-Stream Transport (MST) can drive two displays from a single USB-C port. Apple built MST into some Macs, but the 12-inch MacBook lacks it, and thus can only handle one external monitor. Thunderbolt 3 has more robust display support, enabling it to use higher refresh rates and manage significantly more pixels overall.

Thunderbolt 3 cables are labeled with the same lightning logo used by Thunderbolt 2 cables, while USB cables with USB-C connectors show the familiar USB logo and may also be branded with SS+ for SuperSpeed+. Older USB 3.0 (also known as USB 3.1 Gen 1) cables are sometimes also branded with an SS for SuperSpeed.

Happily, Thunderbolt 3, as supported by the new MacBook Pros, supports all the protocols handled by USB-C, plus Thunderbolt and FireWire. The end result is that nearly any device can be plugged into a Thunderbolt 3 port, with the correct cable, adapter, or dock, as I explain next.

(What kinds of ports are you using with a Mac laptop? You can fill out my survey and see the current results.)

Adapt or Die! -- There’s both some FUD and reasonable caution about USB-C cables and adapters. Quality gear comes from the likes of Apple, Belkin, Google, and Kensington, although Apple’s products have historically been quite expensive. Apple recently cut prices of all its USB-C and Thunderbolt 3 accessories through 31 December 2016; see “Responding to Complaints, Apple Drops Adapter and Monitor Prices” (4 November 2016).

You can often find less expensive gear made cheaply by little-known manufacturers and sold via Amazon (see “Be Careful When Buying Apple Accessories on Amazon,” 24 October 2016). Before buying from unfamiliar brands, I recommend that you consult Google engineer Benson Leung’s Amazon reviews, whether or not you make the purchase via Amazon. He has extensively tested cables, adapters, and other equipment in his personal time, and he can steer you towards and away from USB-C products.

Let’s assume you have or are planning to get a new MacBook Pro with Thunderbolt 3. Here’s a rundown of what you’ll need for each of the various connection types:

  • USB: For connecting older USB peripherals, you’ll need a USB-C adapter, cable, or dock. Existing products will work fine with the MacBook Pro models. If you want the simplest one-to-one converter, pick up a USB-C to USB Type-A adapter — or several. Apple’s adapter is $9; well-reviewed adapters on Amazon cost a couple bucks less.

    My favorite dock is currently the Satechi Aluminum Multi-Port Type C Adapter, which I gave top marks to in a review at Macworld. It offers a 4K display output (via HDMI, compatible with DisplayPort), two USB 3.0 Type-A ports, and pass-through power. It held up well in testing, and it’s an attractive, compact unit.

  • Lightning: If you want to charge a Lightning-equipped device without using an adapter or dock, you can get Apple’s USB-C to Lightning cable, available in 3.3 foot/1 meter ($19) and 6.6 feet/2 meters ($29) versions.

  • Ethernet: To add gigabit Ethernet, which many people prefer over Wi-Fi when it’s available at a home or business office, you have plenty of options with USB-C now. Don’t overpay: the $17 Kanex adapter fits the bill. Like many USB to Ethernet adapters, it requires a free driver for the Mac. (Thunderbolt 3 uses the 10 Gbps Ethernet specification for peer-to-peer transfers between two computers using a Thunderbolt 3 to Thunderbolt 3 cable.)

  • FireWire: If you have older equipment that supports FireWire 400 or 800 as its only or fastest communications method, you may need to wait to see what materializes. There’s no direct adapter or cable available. Apple’s FireWire 800 to Thunderbolt 2 adapter would then have to pass through a Thunderbolt 2 to Thunderbolt 3 adapter (see below), a combination that hasn’t yet been tested for reliability, but which Apple says is supported. Some Thunderbolt 2 docks include FireWire ports, and an updated version of one of those could be the right path.

  • Thunderbolt: Because Thunderbolt 3 is backward compatible with the previous version, Thunderbolt 2 docks should work fine. It’s possible there could be incompatibilities with certain chips or features, so you may want to wait for others to test and report on them. Roman Loyola at Macworld rounded up the best Thunderbolt 2 docks in December 2015.

    Docks will require a Thunderbolt 2 to 3 adapter ($29). Unfortunately, that adapter doesn’t allow for connections to Mini DisplayPort displays like Apple’s older Cinema Displays, although it should work with the 27-inch Thunderbolt Display. By the way, Thunderbolt 3 to Thunderbolt 3 cables are currently a little pricey: Apple is selling two Belkin cables: $22 for 0.5 meters (1.6 feet) and $52 for 2 meters (6.6 feet).

    Belkin has announced a Thunderbolt 3 dock too. The Thunderbolt 3 Express Dock HD is a refresh of a previous version that cost about $250. It will sport pass-through power (up to 85 watts, enough for any MacBook Pro model), two Thunderbolt 3 ports, one full-size DisplayPort jack, gigabit Ethernet, two analog audio jacks, and three USB Type-A 3.0 ports. It can handle two monitors, each up to 4K, by using one Thunderbolt 3 port and the DisplayPort connection. A lot more Thunderbolt 3 docks are coming.

    For more details on other adapters and cables, consult Roman Loyola’s recently posted Thunderbolt 3 adapter guide at Macworld.

  • Displays: On the monitor side of the equation, you should be able to use all displays, up to 4K resolution, that support DisplayPort 1.2 or later. You’ll need a USB-C to DisplayPort adapter or cable. An increasing number of monitors offer DisplayPort over USB-C as an option — sometimes the only option (see, for instance, “Acer H277HU USB-C Display Is an Affordable MacBook Companion,” 11 April 2016). However, 5K displays will need native Thunderbolt 3 support, as with the new LG 5K monitor Apple showed off in its keynote and which it will be selling in Apple Stores.

    Apple just dropped the price on its previously expensive USB-C multiport adapters, both of which offer video out, along with a USB-C power-only port for passthrough charging and a USB Type-A port. The Digital AV Multiport Adapter with HDMI and the VGA Multiport Adapter are both $49, at least through the end of 2016, after which the price may return to $69. You can also get a variety of USB-C to DVI adapters from other parties, though we don’t have a particular recommendation.

    The 13-inch MacBook Pro models have built-in video support for one 5K display or two 4K displays. The 15-inch models can handle two 5K displays and a whopping four 4K displays. That’s because the 13-inch models have one USB-C controller and a perfectly fine video system; the 15-inch models include two USB-C controllers and much better display circuitry.

Real-World Scenarios -- Now that you know what the adapter options are, how do you apply them? There are two notable scenarios: moving data to a new MacBook Pro via the Setup Assistant or Migration Assistant, and working with Target Disk Mode.

Apple has published a support page explaining the possibilities for migrating data to a 12-inch MacBook or late-2016 MacBook Pro; also be sure to read “How to Migrate to a New Mac” (14 September 2016). Depending on the Macs in question, Apple suggests a few choices:

  • Wi-Fi: Apple suggests that Wi-Fi is the simplest method, but it’s by far the slowest, and in our experience, it often fails in the middle. We recommend Wi-Fi as the last-ditch method.

  • From a backup drive: If you have a backup of your previous Mac, either a bootable duplicate or a Time Machine backup, you can attach that drive to the new MacBook Pro via USB-C.

  • Ethernet: With a USB-C to Ethernet adapter for the new MacBook Pro, and another adapter for the older Mac if necessary, Setup/Migration Assistant can transfer your data over a standard Ethernet cable.

  • USB-C: If you’re migrating from a 12-inch MacBook to a new MacBook Pro, a USB-C to USB-C cable will work. Not all such cables have full data transfer capabilities, so make sure to get one that does, such as this one from Belkin.

Target Disk Mode, a way to turn one Mac into a bootable drive for another Mac, is a somewhat different situation. Apple has updated its Target Disk Mode page to include a mention of Thunderbolt 3. Apple is light on the specifics but seems to imply that you will need two matching ports and a cable to connect them. From this reading, only the 12-inch MacBook and the new MacBook Pros will be able to employ Target Disk Mode between themselves, using either a USB-only USB-C cable or a Thunderbolt 3 cable.

However, Target Disk Mode also reportedly worked with a Thunderbolt 2-to-FireWire adapter, so that combination may also work with an additional Thunderbolt 2-to-3 adapter, but we haven’t yet seen confirmation.

USB-Cing Stars -- This may all seem confusing initially, but it should pass quickly because everything on the market for USB and DisplayPort over USB-C today should work with Thunderbolt 3. The main group that will be disappointed are those who buy Thunderbolt 3 peripherals and expect them to work with a 12-inch MacBook, which doesn’t extend USB-C support to Thunderbolt. We can hope that Apple makes Thunderbolt 3 standard across the entire Mac line.

I anticipate that, now that Thunderbolt 3 is out and available in a mainstream Mac, other manufacturers will ship more new high-end computers with Thunderbolt 3 and USB-C. USB 3.1 Gen 2 tops out at 10 Gbps, which will be fine for lower-end systems, which don’t require 40 Gbps performance and aren’t intended to support more than two displays. Mobile devices outside of the Apple ecosystem will stick with and continue to adopt USB-C without Thunderbolt 3 for simplicity, power consumption, and controller cost.

With nothing else like either USB 3.1 Gen 2 or Thunderbolt 3 on the horizon and the broad industry support of the USB-C connector, USB is finally living up to the Universal part of its name — even when Thunderbolt is thrown in on top.


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Comments about Explaining Thunderbolt 3, USB-C, and Everything In Between
(Comments are closed.)

Simon  An apple icon for a TidBITS Contributor 2016-11-04 00:48
Very useful guide. Thanks, Glenn.

You mention USB-C to DisplayPort cables. What about HDMI? Are there or will there be such cables, or do I need to resort to Apple's "Digital AV Multiport Adapter"? (assuming I don't have a TB3 dock with built-in HDMI)

For Ethernet adapters I prefer Apple's so I don't have to worry about 3rd party drivers. But Apple so far only offers TB2 to Gigabit. Would that work in combination with a TB2 to TB3 dongle?
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-04 01:28
Lots of USB-C to HDMI adapter/dongle options. Google has one even. And it's a standard feature of most docks.

As for Ethernet, I've found some that require a driver for full functionality (wake from sleep) and others that require a driver to work at all. I'd definitely read reviews for USB-C to Ethernet adapters, and see what other Mac owners say.
Plugable has stated their USB-C to HDMI adapter behaves inconsistently--this is apparently unrelated to the Thunderbolt 3 chipset compatibility issue ( I wonder if similar HDMI adapters from StarTech or Monoprice will have issues.
Simon  An apple icon for a TidBITS Contributor 2016-11-08 05:40
Thanks to another kind poster I was pointed to this support ducument:

It clearly mentions the Gigabit-TB2 adapter can be used on a new MBP in conjunction with Apple's new TB3-TB2 dongle.
bitguru  2016-11-04 16:31
There were strong rumors at the time that the type-C connector was actually developed by Apple and given away so that it would be adopted widely for USB and Thunderbolt.
Were these ever confirmed or debunked?
Daniel Compton  2016-11-07 16:03
Unfortunately, it looks like not all Thunderbolt 3 devices will work with the new Macbook Pro, adding more confusion to this situation:
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-07 16:06
We’re waiting for some more clarity about that. Apple hasn’t offered comment, and it’s a single vendor. I would expect to hear from Intel and Texas Instruments, too. We’ll provide more detail when we feel there’s more to go on.
Will daisychaining monitors work over USB C?
The 4K LG monitor just has a few USB C ports, and Apple says they are only 2.0 for some reason. What I'd like to do is connect my 1080p monitor to one of these using a DisplayPort to USB c cable to preserve the one cable with Power to the MBP. So:
1080p DisplayPort-->USB c 4K-->2016 MBP.
Apple support said this was possible but I don't believe them given that daisychaining only works with TB on the Mac, and the 2.0 specifications on the USB Ports. But maybe because this is Apple sanctioned they made it work.

Edit: you do say this: "Though I can’t find a definitive answer, it appears that you cannot daisy chain USB devices connected via USB-C, although you can simulate daisy chaining with the addition of USB-C–connected hubs. "

So if I'm understanding this right, I'd need a USB c dock in the middle? Would the monitor be able to pass power through it to the MBP?
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-07 16:24
My understanding is that works only with Thunderbolt 3 monitors, not USB-C ones. USB-C, from what I can tell, does not support daisy chaining, only hubs. The LG monitor uses so many USB-C "lanes" for 4K DisplayPort that it lacks enough lanes to offer USB 3, thus drops to USB 2 (480 Mbps), which requires fewer lanes.

A Thunderbolt 3 monitor can daisy chain both because the spec supports it and Thunderbolt 3 has enough raw throughput to pass through enough DisplayPort signal. But USB-based USB-C monitors can’t.

Conceivably, a non Thunderbolt 3 monitor could pass through a signal (by acting as a hub of sorts), but the monitor resolution for each connected display would have to be half of 4K (about 1080p or so), and the Mac model would have to support MST, described in the article, which the 12-inch MacBook does not, and the new MacBook Pros don't require as such.
So would a cheap USB C dock in the middle fix this? I'll be docking this laptop every day and want a one-cable solution. If I am forced to buy an expensive TB3 dock anyway, then I'd rather get a cheaper 4K monitor.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-08 11:30
Yes. I've tested USB-C docks with a 12-inch MacBook where you can have a 4K display and get USB 3.1 Gen 1 (5 Gbps) throughput on the USB ports.
Do you have links? All I can find are docks that are limited to 30 Hz. The caldigit can do it with a firmware upgrade but then your USB ports become 2.0.
Andrew  2016-11-07 16:38
Is there a difference between a USB-C to USB-C cable and a Thunderbolt 3 to Thunderbolt 3 cable? I know physically they would appear the same but would they both be capable of transmitting at the same data rate given identical host and peripheral?
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-07 16:47
They will be different electrically and functionally, made to different specifications. Also, every USB-C cable will have a tiny computer in the connector end that negotiates details with the port's controller.

A USB-C cable designed for USB data will work with Thunderbolt 3, even between Thunderbolt 3 and Thunderbolt 3 ports, but the controller will recognize it can only handle USB 2 or USB 3.

A Thunderbolt 3 cable should work with a USB-only port or ports, but will max out at USB 3 speeds (or whatever the controller wants).

USB-only USB-C cables will be marked with a USB logo as noted in the article. Thunderbolt 3 cables will have a lightning bolt icon and a tiny 3.
There are also "active" and "passive" versions of TB3 cables. The latter max out at 20gbps while the former can utilize the full 40gbps rate of TB3. Right now it seems that the active cables are only available in 0.5m lengths but that will change. The passive cables are available up to 2m.
I can verify that Target Disk Mode does work over Thunderbolt 2 to Firewire adapters. We used it to image 2011 Mac Pros to 2013 Mac Pros.
Jim Vance  2016-11-07 18:48
What does "but not vice versa" mean in this context? Re-writing or adding a clarifying note would be most welcome. Thanks.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-07 19:05
I don't see that phrase in this article, so I'm not sure to what you're referring?
Jim Vance  2016-11-08 16:12
Sorry, this phrase is in the summary of the article that one sees on the tidbits home page. It reads as follows:

Explaining Thunderbolt 3, USB-C, and Everything In Between

The new MacBook Pro laptops are the first Macs with Thunderbolt 3, a standard that uses the USB-C plug style and retains USB compatibility, but not vice versa. But what’s most interesting about Thunderbolt 3 is how it supports numerous other protocols, including USB, Thunderbolt 2, FireWire, DisplayPort, and Ethernet, with the addition of appropriate adapters.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-08 16:42
Oh my goodness; that doesn't show up on the article page. I'll discuss tweaking it with editors.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-08 16:42
Oh my goodness; that doesn't show up on the article page. I'll discuss tweaking it with editors.
Amit Udeshi  2016-11-07 19:38
One option you haven't mentioned that works at least in Tokyo. Take both old and new mac to Apple Store and they will use their spare adapters, chargers, etc. to help migrate (typically ethernet option)
Great, well done. It helps me a lot. My very thanks!
Dennis B. Swaney  2016-11-07 20:09
Glenn, OWC has a new Thunderbolt 3 Dock available for pre-order:

It has a FW800 port, SD card reader, mini DisplayPort, 5 USB-A 3.1 Gen 1 ports, etc.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-07 21:44
This article isn't exhaustive—there will soon be way too many things to list. So we are unlikely to update it to add more options, but will probably write more about different angles, like docks, etc.
Michael Paine  2016-11-08 01:15
Satechi are about to release a USB-C adapter packed with more ports:
EThernet, HDMI, SD cards, USB3 & USB-C pass-through
Michael Paine  2016-11-14 22:18
Received my Satechi "Multi-port" adapter today - fast postage from USA!

Most things seems to work well: HDMI, USB, ethernet... The Macbook connects to internet via ethernet and I can access a Time Capsule HD but, strangely, Network Diagnostics report a local network error. Only disappointment is that my iPad won't charge (it will with the Apple HDMI adapter).

It should be great for travel and also as a dock for the office (just one cable to plug into the Macboook to connect internet, USB, HDMI and power).
Simon  An apple icon for a TidBITS Contributor 2016-11-15 00:00
This is one of my main gripes with USB. The power rating always seems to be hit and miss. And of course it doesn't help that hardly a hardware manufacturer openly states what power each and every port can deliver.

The MBP's USB-C obviously offers enough juice to charge the iPad. So my guess is that the USB-A ports on the Satechi do not pass through the full 2 Amps (or similar) that USB-A can. Bummer.

It would be interesting to see if you can at least charge the iPad if you hook it up to the Satechi's USB-C through a Lightning-to-USB-C cable.
Michael Paine  2016-11-15 02:43
At least my iPhone charges OK. That is my main travel requirement. Not sure what you mean about Lighting-to-USB-c cable.
Michael Paine  2016-11-15 20:10
Also the SD slot & micro SD slot are handy. They turn the adapter into a memory stick.
Wibbly  2016-11-08 03:47
Apple has a support document that provides details on which adapters can be connected together to provide which protocols. In particular, I had a need for Firewire and the note says you can chain the Thunderbolt3-Thunderbolt2 adapter and then add the Thunderbolt2-Firewire adapter

Here is the document:
Could you please add information about the HDMI 4K adapters whether they support 60Hz (good) or only 30Hz (toy)?

The Satechi adapter can only support 30Hz, which makes it a no-go option for me.

Since TVs are way more affordable than monitors, people which do not want ultra-sharp displays like the new LG 5K 27" and 4K 21" but more screen space might want to connect one or two 40" curved 4K TVs via HDMI 2.0 as computer displays and show unscaled 3840 pixels (I currently type this on a LG 34" ultrawide 21:9 monitor with 3440*1440 px, unscaled, which is already 2 years old, and of course I want MORE space on my next monitor...).
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-08 11:47
It depends on the controller. The 12-inch MacBook only supports 4K at up to 30 Hz (and only 3840 by 2160). The MBP models support 4K (4096 by 2304) and 5K at up to 60 Hz.

We'll be writing follow-up articles; this piece would get ungainly if we kept adding to it.
Right - the MacBook 12" is no Pro, and has weak graphics. It supports only a single external 4K display with 30Hz.
But the Pro line supports 60Hz (13" max two displays, 15" up to four 4K displays), so please check all HDMI adapters for that.
rolf786  2016-11-08 06:06
Could Apple (or someone) make a Magsafe to USB-C charging adapter dongle, similar to the Magsafe 1 to Magsafe 2 adapter they did? That way you could make use of your spare laptop charges AND you'd still get protection against tripping over your charging cable.
Adam Engst  An apple icon for a TidBITS Staffer 2016-11-08 10:27
Griffin Technology has one, but it still sticks out of the Mac, so it's not quite the same thing:
rolf786  2016-11-15 03:19
Griffin have their own adapter format (and reviews say it's not that nice as magsafe). I was thinking specifically of a Magsafe-compatible dongle (I have quite an investment in Apple laptop chargers!) but I wasn't sure if the voltage/current it provides is compatible with USB C charging.
Michael Brown  2016-11-08 08:43
"...Thunderbolt 2 to 3 adapter ($29). Unfortunately, that adapter doesn’t allow for connections to Mini DisplayPort displays like Apple’s older Cinema Displays"
Wait what? So I won't be able to plug my Dell display into a TB 2 to 3 adapter via a mini Display Port cable? That's what I got it for :-(
Simon  An apple icon for a TidBITS Contributor 2016-11-08 09:04
It will still work, just with a cable instead of a dongle. If you take a USB-C/TB3 to (m)DP cable you should be fine.

Here's an example.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-08 11:48
Exactly. DisplayPort is native to USB-C and part of Thunderbolt 3 (for higher resolutions). So you don't need to use a Thunderbolt 2 to 3 converter at all. You can use a dock or a cable or an adapter, and plug from USB-C directly to a DisplayPort or HDMI connection.
Michael Brown  2016-11-08 15:08
As I already have a Thunderbolt to Ethernet adapter I was hoping to kill 2 birds with one stone with the TB 3 to 2 adapter, allowing me to use my old TB to Ethernet *and* for hooking up my external display (not at the same time of course).

Looks like I'll have to get a USB-C to DP cable / adapter then :-(
Do you know if it's possible to connect the old Apple Cinema Display (ACD) to a 2016 MacBook Pro? The ACD has a built-in cable with a male mini DisplayPort at the end. Would a female-to-female DisplayPort adaptor and a Thunderbolt 3/USB-C to male mini DisplayPort cable work? Or does this adapter actually support the ACD: The Amazon reviews are mixed and it's USB-C rather than Thunderbolt so who knows what it supports?!
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-10 15:09
It's a tricky question. We know that the Thunderbolt 2 to Thunderbolt 3 adapter doesn't work with DisplayPort. We know that DisplayPort is native to USB-C and by extension to Thunderbolt 3. We know that full-sized DisplayPort to USB-C and HDMI to USB-C adapters and docks work!

But there's apparently something funny with the Apple Cinema Display. I reviewed a dock at Macworld by the folks at Nonda with explicit ACD support, and they said because of chip issues, they could only support the 2015 MacBook (not the 2016) and only the ACD (not the Apple Thunderbolt Display). They were stymied.

Any USB-C adapter will work with a Thunderbolt 3 system, though, through backwards compatibility. So if it worked with USB-C that lacks Thunderbolt 3 it'll work with Thunderbolt 3 as well.
Thanks for the response, Glenn! Sadly my 2016 Macbook Pro still hasn't arrived (I was late to order and it's not due until mid December), but it looks as though, whilst the number of potential options for connecting the Cinema Display continues to expand ( ) there are still many complications with the ACD and the mini DP adaptors. See, for example, the Amazon reviews of the Juiced Systems USB-C Multifunction Display Adapter. By far the most promising so far is this: but I'm still a little skeptical as it's only the seller who's confirmed that it works with the 2016 MBP.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-27 18:25
A lot of these products look like prototypes and aren't shipping. Some note only MacBook 2015 compatibility. It's going to be a mess!
This is starting to look promising: the first non-seller review of the aforementioned "CY USB-C USB 3.1 Type C to Mini DisplayPort DP" adaptor working with the 2016 MacBook Pro is in!
Thanks Glenn, this is great and an awesome roadmap. One thing that I may have missed is will this work with the original USB 1. As a photographer I have stashes of old hard drives and a Zip drive stored away. I've moved them all to larger drives but keep the old as backups. I can see a day where those are no longer accessible and it may be today with USB C.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-08 11:49
USB 1 has largely been abandoned, so I'd recommend making additional copies, maybe writing to permanent discs and sticking in a safe-deposit vault. Zip disks are only rated to last a few years, so they may have degraded beyond readable point, in any case. Old hard drives magnetic properties degrade over time, too.
Michael Paine  2016-11-09 15:43
I use 25Gb bluray disks for long-term backup of crucial data. I realise typical photo libraries now exceed this capacity but the really important stuff should fit. Unlike DVD and CD (and magnetic media, and SSD!) Bluray is designed to last for decades. The biggest problem may be finding a Bluray drive in 2030!
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-09 15:50
Good plan! Although 1 TB SSD with a USB 3 interface might be a good investment when it gets cheap enough.

Treat your USB 1 and Zip drives as quaint artifacts, rather than backups.
Apple sells a multi AV adapter to connect the new MacBook Pro to HDMI monitors, but I wonder if it would also allow an Apple TV to connect to a Thunderbolt 3 monitor.

Is it possible to connect devices with HDMI out (Apple TV, PlayStation 4) to Thunderbolt 3 monitors (LG UltraFine 4k/5k) with a (combination) of cables or dongles?

I thought it might work if the monitor supports "DisplayPort Alternate Mode on USB Type-C Connector Standard", _and_ you buy an active (and relatively expensive) HDMI to DisplayPort adapter, and chain the DisplayPort to USB-C Thunderbolt 3 somehow. However, is DisplayPort Alternate Mode on USB Type-C something that an input such as a monitor can accept or is it only an option if the output (e.g. a MacBook Pro) supports it?

I'd be interested in a Thunderbolt 3 monitor if it could be used for more than only the new MacBook Pro.

This article mentions that only the LG 5k monitor requires Thunderbolt 3 sources. Does that mean it might work with the 4k monitor?
Curtis Wilcox  An apple icon for a Friend of TidBITS 2016-11-11 10:41
As you've found, HDMI - DisplayPort adapters are not bidirectional. Adapting a DisplayPort source to an HDMI display requires a cheap and relatively simple adapter but adapting an HDMI source to a DisplayPort display requires expensive, complex hardware. My hunch is once you've converted to some kind of DisplayPort, converting it further to DisplayPort Alternate Mode on USB-C is feasible. The LG 4K monitor is not a Thunderbolt 3 device so it's more likely to work.

I think it's better to wait and see what other products come along, a 4K monitor with both USB-C and HDMI interfaces would be much simpler to work with.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-11 13:03
What Curtis said! Thanks for providing all that detail.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-11 13:06
A monitor that only features a USB-C connection (either built in or a connector into which to plug a cable) will only work over USB-C.

A monitor with Thunderbolt 3 as its only connection method (such as the 5K) will only work with Thunderbolt 3.

However, we're like to see monitors that offer DisplayPort, HDMI, and USB-C, as there's no real reason not to—all three standards can support 4K, and it lets a monitor maker sell to a broader audience. Internally, I don't think very much more circuitry is needed, because it's all effectively DisplayPort just being routed out of a controller.
How much bandwidth does it take to drive a 4K display at 60Hz? Could there be a hypothetical USB-c hub that connects to a single MBP USB-c/TB3 port and drives two 4K at 60 Hz + 1Gpbs Ethernet + a couple of USB-3.1 ports, simultaneously?
Curtis Wilcox  An apple icon for a Friend of TidBITS 2016-11-12 15:05
A single UHD@60Hz* display is effectively 17.28 Gbit/s but it's not like the connector has a bandwidth budget that's partially consumed by video and by other devices using USB, it's more complex than that.

The announced OWC *Thunderbolt 3* dock can do all that.

However when the source port is a USB-C connector that does not support Thunderbolt 3, only USB 3.1, I expect the options are more limited. The video is separated from the USB-ness, it's DisplayPort Alternate Mode. DisplayPort 1.2 introduced "Multi-Stream Transport" (MST) which allows daisy-chaining monitors or having a hub. However, DisplayPort 1.2 can't be used for 2 4K/UHD displays and no Mac supports 1.3 yet. As Glenn wrote, the 12-inch MacBook doesn't support MST. Apple will probably stick with Thunderbolt 3 so what USB 3.1 supports won't matter to them but at least some PC manufacturers probably won't adopt Thunderbolt 3 and we'll see what docks and display hubs they come up with. Dell already made the D3100 which supports 1 UHD and 2 Full HD monitors on a single USB connection.

* Often when people say "4K" they really mean UHD; UHD is 4 times more pixels than Full HD, 1080p, it's 3840x2160. "4K" is a wider, more cinematic resolution, 4096×2160. This may be one of those cases where the mis-use becomes so common that we just have to accept it, like "literally."
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-12 15:44
USB-C has "lanes," which get allocated, so it's not per se about bandwidth. Thunderbolt 3 supports 40 Gbps of data in each direction, but it has to be carved up and assigned to pins, essentially, which introduces limits so you can't make maximum use of the 40 Gbps with a mix of devices, depending on the mix.
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-12 15:46
Yes, this is what's confusing is that DisplayPort is both an alternate mode that works on USB-C without Thunderbolt 3 and (according to Intel's explanation) DisplayPort is incorporated inside Thunderbolt 3 separately. So a 5K monitor via Thunderbolt 3 is technically using Thunderbolt 3 alternate mode and DisplayPort inside that, while a 4K connected to any USB-C is using DisplayPort in alternate mode directly.
Openreels  An apple icon for a TidBITS Contributor 2016-11-12 12:16
Gawd this is a mess! What we really need is a "USB-C Ecossytem" diagram that shows all the various sub-connections and how they relate (ie" what can carry, or is compatible with, what). I'd make one myself if I could get it all straight!

Here's a resource that might be helpful:
Glenn Fleishman  An apple icon for a TidBITS Staffer 2016-11-12 15:46
That's an excellent idea.
Steve Nicholson  2016-11-18 09:41
I was SO looking forward to the new MacBook Pros to replace my aging 2009 model (with maxed-out RAM and SSD to replace the optical drive). But between dropping every port I use, this USB-C transition period, the jacked-up price, and zero expandability, these new machines hold no appeal for me. I've decided I can use my iMac as my main machine and get by with my iPad and a keyboard when I'm out and about.

My wife also has a 2009 MBP which is her only Mac and needs replacing. To save her from the USB-C transition, I'm ordering her a refurbished 2015 13" MBP.