USB is easy. Please forgive my pun, but you know what I mean. USB used to represent a type of connector for computers: Type-A, which is flat, rectangular, and has a correct orientation. Peripheral devices either have a directly wired wire or have a B-type USB port: blocky, almost square, and have only one correct orientation.
However, in the process, we have accumulated some other products: Mini-B, a thick trapezoid used by Texas Instruments (TI) graphing calculators, early Amazon Kindles and other devices; Micro-B, a thin trapezoid , Becoming the de facto charging shape for mobile devices, headsets and other battery-powered hardware. More obscure connectors have also appeared, such as the wide and oddly shaped USB 3.0 Micro-B most commonly found on external hard drives.
After the release of the USB 3.1 standard, the evolution of the USB-C connector promised simplicity. Unlike the host device Type-A and the peripheral devices Type-B, Mini-B, Micro-B, etc., a single connector is suitable for both ends of the connection and carries power and data at the same time. Electricity can flow in either direction through the same cable: a computer that charges a battery or cell phone; a battery that charges a computer. Its long axis is also reversible, so it is impossible to insert it in the wrong direction.
The hardware work is excellent: the USB-C plug fits any USB-C jack. But maybe the USB Implementers Forum (USB-IF), the organization responsible for the development of the USB standard, did not fully consider the complexity of the USB wiring and how to communicate effectively: power and video plus several different data standards .
The problem is that USB-C has become a connector for very different purposes, and a glance at a port or cable rarely tells you enough information to understand what happens when the cable is plugged in. USB-C connectors are supported by USB 3.1 and 3.2 (but not required), and are required by USB 4 (and Thunderbolt 3 and 4), even though they were intertwined different standards before the 4th edition of each specification .
Plugging in the USB-C cable may cause various problems. Will you get the maximum speed between the two devices? Can you get the wattage needed to power a computer or charge a USB battery? Nothing will happen, don’t know why? It is often impossible to know that even the packaging that the cable discarded a long time ago actually contains all these answers, because you also have to understand the ports on both ends.
Most of the confusion we all face stems from the fact that all actions occur deep inside the computer, mobile device, or peripheral device. No matter what data or power function a USB-C port can provide to another device through a cable, it depends on the host or peripheral controller, a set of chips, and power management circuits that implement USB, Thunderbolt, and other standards in the hardware. The controller can range from a standalone module added to the motherboard to deeply integrated into a system-on-chip like Apple’s M1.
A cable is an external intermediary between two devices; it only knows to carry data, but not to encode or decode data. The tip of the cable informs the devices at both ends of the type of data it can transmit from one end to the other. This relies on the microchip built into each USB-C plug. (Many other types of plugs, such as USB 3.1 Type-A and Lightning, also contain chips, which is one of the reasons why cables are more expensive than before.) Controllers can transmit different standards on the same “line”, and they rely on Cables to help them negotiate the best common method for talking to each other.
The problem is that we usually don’t know what protocol set each device is talking about. Even if we do, we may not be sure whether the cable will allow them to talk as fast as possible—or in rare cases, we don’t know at all. For example, Apple still provides so-called USB-C charging cables (designed in the early days of USB-C) along with many types of laptops. It is fully compatible with the USB-C specification and can carry up to 100 watts of power, but it does not support video and only transmits data at a speed of 480 Mbps (USB 2.0)! Apple’s Thunderbolt 3 cable can carry the same maximum power, as well as video and 40 Gbps data for Thunderbolt 3 and 10 Gbps data for USB 3.1.
What we want is to look at the ports and cables and understand what they do. It shouldn’t be difficult, but judging from the graphics released by USB-IF in late September 2021, it is obviously like this, which shows the new label of the power wiring standard. This simple diagram reveals the amount of chaos that organizations might have anticipated, as well as past and present challenges.
The benevolent see benevolence. Let me help solve the USB-C confusion: how did we get here, where are we, and what we hope for the future.
USB Type-C, almost collectively referred to as USB-C, attempts to solve multiple problems that have plagued USB hardware connections for decades, because USB data standards range from 1.5 Mbps and 12 Mbps (1.0 and 1.1) to 480 Mbps (2.0) in one direction Up (less in the other direction) to symmetrical 5 Gbps data transmission (3.0).
As shown in the figure below, through Wikipedia, all connectors that appeared before USB-C may have significant restrictions on the connector at the other end. Type-A is the closest match, but please note that Wikipedia’s “proprietary, dangerous” label for USB Type-A to Type-A cables is defined as “not interoperable with USB-IF compatible devices and may be inserted Two devices will be damaged.”
Before USB-C, a Type-A cable on one end or an adapter might have one of four other types of connectors on the other end, but you could not have a Type-A to Type-A cable. In contrast, USB-C is suitable for both ends of the connection, and it supports five other plug types: Type-A and four Type-B connectors.
USB-IF first introduced USB 3.1 in 2013, increasing the maximum speed of Type-A from 5 Gbps to 10 Gbps, and paved the way for the introduction of USB-C connectors in 2014. This connector type debuted in a limited set of devices in 2015, including the now discontinued 12-inch MacBook, which only comes with a USB 3.1 controller and requires a USB 3.1 video adapter to connect to an external display.
It is best to use these concise and sensible words from Wikipedia to introduce the following content: “Type-C connectors are common to multiple technologies, but only some of them are mandatory.”
The USB-C connector was originally only available for USB 3.1. It has Gen 1 and Gen 2 versions, called SuperSpeed (5 Gbps) and SuperSpeed+ (10 Gbps), respectively. 3.1 The standard appeared shortly before USB-C, and its 5 Gbps and 10 Gbps speeds do not require USB-C: they work on Type-A, Type-B and Micro-B, and USB-C.
In 2017, USB-IF released the 3.2 specification, which allows 10 Gbps through USB-C and earlier connectors through a USB 3.2 controller in a computer or mobile device, and 20 Gbps through USB-C only. The trade organization abandoned some early naming conventions and suggested using attractive names such as “SuperSpeed USB 5Gbps”, “SuperSpeed USB 10Gbps” and “SuperSpeed USB 20Gbps”.
The organization’s language usage guidelines state (is it useful?), “USB 3.2 is not a USB Type-C, USB Standard-A, Micro-USB, or any other USB cable or connector.”
Thunderbolt is also involved. As the successor to FireWire, Apple adopted Intel’s Thunderbolt standard early on, but the first two versions of Thunderbolt have never been widely adopted. The reasons for the poor performance include USB becoming more popular, USB 3.0 supporting 5 Gbps speeds early enough, and Apple is still the only single-chip computer manufacturer that has not competed in terms of pricing and commercialization. Purchasing a higher-speed bus card or a specific PC or server computer configuration that supports Thunderbolt may make sense for a specific user or market segment, but not for the entire non-Mac industry.
But Intel has taken a key move, possibly in cooperation with Apple: In addition to doubling the data rate to 40 Gbps, Thunderbolt 3 will also support USB-C connections, relying on what the USB-IF trade organization calls an alternative model. The alternative mode is not to transfer USB 3.1 or 3.2 data via USB-C, but to allow other standards to be encapsulated. It is a second language of USB: in alternate mode, the Thunderbolt 3 USB 3 controller can use a Thunderbolt 3 compatible cable to communicate with the native Thunderbolt 3 controller. They don’t even need to know that they are speaking different languages. (Intel’s Thunderbolt 3 controller uses a similar method to be backward compatible with USB 3 and earlier, but the Thunderbolt 3 cable is still required.)
DisplayPort has an alternate mode and HDMI has a video transmission: this is how a 12-inch MacBook can transmit video via USB-C. The other one enables PCI Express for high-speed data transfer, and an external GPU for computers that support it, and the last one is for Thunderbolt 3.
One more thing: USB-IF released USB 4 in 2019, and Intel released Thunderbolt 4 in 2020. USB 4 provides an optional implementation of Thunderbolt 3 in the USB specification, and Thunderbolt 4 has a mandatory requirement to support USB through USB 4. Devices that clearly support USB 4/Thunderbolt 4, such as Apple’s 14-inch and 16-inch M1 Pro and M1 Max MacBook Pro models, can use almost all existing cables and adapters to handle various types of Thunderbolt and various types of USB. (USB 4 support for Thunderbolt 3 is optional for the host controller, but mandatory for USB 4 hubs, just to make things more confusing. However, I hope that major computer and device manufacturers include USB 4 /Thunderbolt 3 or USB 4/Compatible with Thunderbolt 4.)
Thunderbolt 4 also requires all certified controllers to allow Thunderbolt hubs to add USB-C ports that support up to 40 Gbps, external displays, etc. through any Thunderbolt port on the computer. For Thunderbolt 3, hubs are optional, and some operating systems and computers eventually allow them to be used. You can plug a Thunderbolt hub into a device using Thunderbolt 3 (Apple added this feature in macOS 11.1 Big Sur for all Intel and M1 Macs) or Thunderbolt 4. Thunderbolt 4 also allows display resolutions higher than 8K.
USB 4 requires USB-C for all connections and a minimum data throughput of 20 Gbps, but it can also support the full 40 Gbps of Thunderbolt 3 and 4.
Cable length is also important. Thunderbolt 3 and Thunderbolt 4 cables are passive and active: passive cables can carry 40 Gbps up to 0.5 meters and 20 Gbps up to 2 meters; active cables can transmit 40 Gbps data up to 2 meters. USB 3 and 4 cables can transmit 10 Gbps at up to 2 meters and 20 Gbps at up to 1 meter, but the 40 Gbps flavor is only available for cables up to 0.8 meters in length.
(Unless you need maximum throughput, don’t overemphasize these cable lengths. USB 4/Thunderbolt 4 controllers can use overly long cables at speeds below 20 Gbps or 40 Gbps or are not designed for these speeds: these versions 4 The standard is backward compatible with USB 2.0 and Thunderbolt 1.)
USB 4 is also mandatory to support Power Delivery. As the USB 3.2 guide dryly pointed out, “USB 3.2 is not USB powered or USB battery charging.” Power delivery? Charging batteries? These are two other USB standards that have led USB-IF to meet the labeling chart described in this article.
USB power supply can be traced back to the earliest days, but power is usually limited without the involvement of proprietary controllers and protocols. USB-C marks the first large-scale availability of high-power cables, which are interoperable on many devices. The standard that allows this is called power supply.
A USB-C cable that supports Power Delivery 2.0 and 3.0 should be able to pass at least 60 watts (3A at 20V), but it can also be designed to be 100W (5A at 20V). The USB-C ports on the host and peripheral devices can be designed to be even less-as low as 7.5W (1.5A at 5V) or 15W (3A at 5V). Power Delivery 3.1 adds a higher voltage at the same time as 5A, allowing up to 240W (5A at 48V). The 240W cable requires a new extended power range (EPR) cable type.
Despite the cable requirements, you may see that the cables sold seem to only promise a maximum of 15W. These may be 60W cables sold with devices that consume 15W of power, such as Belkin USB-C chargers, or they may just be non-compliant.
Power Delivery 3.1 also supports fast charging, but there is currently no trademark or specific label. Proprietary versions exist, including those added by Apple to the latest MacBook Pro models. Fast charging requires the 96W charger for the 14-inch MacBook Pro or the 140W charger that comes with all 16-inch MacBook Pro models. (The entry-level model of the 14-inch MacBook Pro comes with a 67W charger, and buyers can upgrade to 96W for $20.)
Using these chargers, macOS will automatically charge MagSafe 3 (14-inch and 16-inch MacBook Pro models) or USB 4 (14-inch only) with the highest available power, allowing a depleted Mac in 30 minutes. Using a 67W charger with a 14-inch MacBook Pro or a USB 4 port with a 16-inch MacBook Pro limits the charging to “regular” speed, which is a bit slow. (In addition, all devices equipped with lithium-ion batteries will control the charging speed above 80% to prevent overheating.)
Finally, the USB battery charging specification enables a strange missing feature: the device plugged into the battery pack does not have a standard USB command, it can issue a simple question, “How much current can I draw?” Always compatible solutions that limit charging between certain devices.
When it comes to charging, you might be wondering: Can I blow up my expensive equipment by plugging in the wrong cable? The answer should be no, and it is almost always the case. The USB-C port and connector negotiate a rate that they both agree on. The previous USB-C and Power Delivery specifications were designed to avoid passing more power than the device can accept, and battery charging upgrades have improved this. (In the early days of USB-C, Google engineer Benson Leung used his spare time to test and record cables, because he found that many cheap cables were poorly made, some of which could even blow up computers or start smoking. Those days now seem to be a long time away. )
Now let us enter the focus of this article. What cable does it do? What can you achieve now? What will the future bring?
The following is a partial list of possible data and power support that you can find in cables with USB-C connectors at both ends:
If this is not unbelievable enough, other less common combinations can be used; the list may be twice or even three times longer. It also does not include proprietary cables, such as Apple’s MagSafe 3 to USB-C cable. How do you distinguish between all these USB-C cables? It depends on whether computer and other equipment manufacturers, cable manufacturers, and peripheral equipment manufacturers correctly mark their parts, manuals, and cable heads in accordance with the various specifications that they claim to comply.
I have collected some examples below, selected from photos on the Internet, and they show how and how wide the cable is marked. It’s worth noting that the marked Thunderbolt 3 cables look very similar-unless you are a snobbery like me and notice the use of many different sans serif fonts.
The following Thunderbolt 3 cables are usually accurately marked: they all have the Thunderbolt icon and the number 3. Most of the things I found are like this, with icons and numbers appearing on both ends of the cable. However, none of these cables indicate whether they are active or passive, nor provide any clues about the wattage they support.
It is easy to find Thunderbolt cables that are incorrectly marked or not marked at all. At least Apple (bottom left) and Universal (bottom center) have a lightning bolt-but there is no 3. So you know it is almost certainly Thunderbolt 3. The StarTech.com cable may have a mark on the other side, but all photos of the cable only show the logo.
When USB 3.1 and 3.2 cables support speeds of 10 Gbps or faster, their tip marks are surprisingly good, although the numbers are small relative to SS. And I don’t even have to use my inner snob to complain that the numbers are sometimes printed in light gray on black, or even gray in different shades of gray.
What you hear about ordinary users and technicians talking and complaining is that the same simple connector can mean many different things, and there is almost no visual way to determine what might happen by looking at ports or cables.
Even if you can find the necessary signs and symbols, you must look for the interaction between ports and cables, data rates, and power. You may even need a magnifying glass to read the printed markings on the cable length to determine the amperage or wattage.
How can USB-IF improve this, especially with Intel’s Thunderbolt team? The label I mocked at first was actually the right direction. With the convergence of USB and Thunderbolt on cross-compatible and backward-compatible standards, there may be opportunities for clarification in the future.
Ideally, USB-IF will also propagate such labels backwards, requiring manufacturers to print the maximum speed and wattage in clear letters. It’s great to see an agreement with Intel that requires manufacturers to mark Thunderbolt cables with a version number and 20 Gbps (long and passive) or 40 Gbps (short and active). This is the strategy adopted by the Wi-Fi Alliance to reduce confusion with 802.11n, 802.11ac, and 802.11ax. They are all “Wi-Fi”: they renamed them Wi-Fi 4, 5, and 6.
In general practice, your best option may be to use old-fashioned adhesive labels after purchasing a cable that suits your needs or opening the cable that comes with the product. Try to get the label manufacturer to put a logo on your cable, or use a cable tie with a permanently marked writable location. Future cables may provide clearer directions, but considering how many cables we have, we are still somewhat self-reliant.
Every week, you will get technical tips, in-depth reviews, and insightful news analysis for discerning Apple users. For 31 years, we have published professional and member-supported technology news to make you smarter.
This is a great article. Last summer, I took my new iPad Air 4 on a short trip, and the USB C cable I carried with me couldn’t charge the damn thing. Even buying something that says “Charge your device” at a local pharmacy won’t work. I kept using the iPad until the battery ran out… When I got home, I tried 4 other USB C cables, and they all can charge the iPad Air 4.
Last summer, I took my new iPad Air 4 on a short trip, and the USB C cable I carried with me couldn’t charge the damn thing. Even buying something that says “Charge your device” at a local pharmacy won’t work.
Post time: Dec-13-2021