USB Type-C and Thunderbolt 3: One port to connect them all

CNET editor Dong Ngo explains USB-C and Thunderbolt 3 and the significance of these peripheral standards.

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USB-C and Thunderbolt 3: One port to rule them all
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Update, August 19, 2016: Added the latest information on USB-C and Thunderbolt 3. This article was originally published on August 22, 2014.

Look around your house and chances are you have at least a few devices that use Universal Serial Bus. On average, some 3 billion USB ports are shipped each year, making it by far the most successful peripheral connection type in the world.

In fact, device manufacturers are so confident in the new USB-C standard that Intel announced last year that Thunderbolt 3, once thought to be a USB replacement, would use the same port type as USB-C. This means every Thunderbolt 3 port will also work as a USB-C port and every Thunderbolt 3 cable will work as a USB-C cable.

Before you can fully appreciate what a leap forward both USB Type-C and Thunderbolt 3 are, let's familiarize you with Type-A, Type-B, and the various versions the Thunderbolt standard.

Thunderbolt

Prior to Thunderbolt 3, Thunderbolt 2 and the original Thunderbolt shared the same cable type and port (which is the same port type as Apple's Mini DisplayPort) and had top data transfer speeds of 20Gbps and 10Gbps, respectively. With these older Thunderbolt standards, the cable was active, meaning the cable itself is a device that requires power to operate so any Thunderbolt 1 or 2 device would require external power in order to function. This made Thunderbolt a much more expensive solution as the cable itself is some 10 times more expensive than a USB cable of the same length.

Thunderbolt Revisions

Revision Year released Super set of Top speed Port type
Thunderbolt 2011 Mini DisplayPort 10Gbps Mini DisplayPort
Thunderbolt 2 2013 Thunderbolt 20Gbps Mini DisplayPort
Thunderbolt 3 2015 Thunderbolt 2 (adapter required,) DisplayPort, PCIe 3rd Gen, USB 3.1 40Gbps (short or active cable) 20Gbps (long, passive cable,) USB-C

Here's how Thunderbolt 3 is different from its predecessors: :

  • The Mini DisplayPort connection type has been ditched in favor of a USB-C connection type
  • All Thunderbolt 3 cables will work as USB-C cables.
  • All USB-C cables will work as Thunderbolt 3 cables as long as they are good quality cables.
  • Thunderbolt 3 has a top data transfer speed of 40Gbps as long as the cable is .5m (1.6 ft) or shorter.
  • For 1m (3.2 ft) or longer cables, Thunderbolt 3 supports passive (cheaper) ones that have a top speed of 20Gbps, and active cables (more expensive) that retain the 40Gbps speed.
  • Thunderbolt 3 is backward compatible with earlier versions of Thunderbolt, but due to the new port type, adapters are required to use legacy Thunderbolt devices.
  • Any USB-C device (like a Nexus 6P phone) plugged into a Thunderbolt 3 port will function normally.
  • Since Thunderbolt 3 devices will use discrete Thunderbolt chips to function, they will not function if plugged into a USB-C port.

All versions of Thunderbolt allow for daisy chaining up to six devices together and in addition to data, can also carry Hi-Def video and audio signals.

USB

In the USB world, things are a bit more complicated because there have been more versions and types than Thunderbolt. Generally, the versions refer to the speed and functionality of the USB cable, while the USB Type refers to the physical shape and the wiring of the ports and plugs. Let's start with the USB Type.

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For the most part, Type-A ends (left of the coin) of the USB cables remains the same across existing USB versions. Dong Ngo/CNET

USB Type-A

Also known as USB Standard-A, USB Type-A is the original design for the USB standard and uses a flat rectangular shape.

On a typical USB cable, the Type A connector, aka the A-male connector, is the end that goes into a host, such as a computer. And on a host, the USB port (or receptacle) where the Type A-male goes into, is called an A-female port. Type-A ports are mostly in host devices, including desktop computers, laptops, game consoles, media players and so on. There are very few peripheral devices that use a Type-A port.

Different USB versions including USB 1.1, USB 2.0, USB 3.0 (more on versions below) currently share the same USB Type-A design. That means a Type-A connector is always compatible with a Type-A port event if the device and host use different USB versions. For example, a USB 3.0 external hard drive also works with a USB 2.0 port, and vice versa.

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Type-A USB port for USB 3.0 (blue) and USB 2.0 on the back of a computer. Dong Ngo/CNET

Similarly, small devices such as a mouse, keyboard or network adapter that have hard-wired USB cables always use Type-A connectors. That's true also for gadgets without cables, such as a thumb drive.

USB 3.0's connectors and ports have have more pins than USB 2.0. This is in order to deliver faster speed and higher power output. However, these pins are organized in a way that doesn't prevent them from physically working with the older version.

Also note that there are smaller Type-A plugs and connectors, including Mini Type-A and Micro Type-A, but there are very few devices that use these designs.

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Popular USB Type-B: From left Standard-B, Mini-B, Micro-B, Micro-B USB 3.0, and Standard-B USB 3.0. Dong Ngo/CNET

USB Type-B

Typically, the Type-B connector is the other end of a standard USB cable that plugs into peripheral device (such as a printer, a phone, or an external hard drive). It's also known as Type B-male. On the peripheral device, the USB port is called Type B-female.

Since the peripheral devices vary a great deal in shape and size, the Type-B connector and its respective port also come in many different designs. Up to now there have been five popular designs for the USB Type-B's plugs and connectors. And since the Type-A end of a USB cable remains the same, the Type-B end is used to determine the name of the cable itself. (Wikipedia has a great USB connector mating matrix you can consult.)

The original standard (Standard-B): This design was first made for USB 1.1 and is also used in USB 2.0. It's mostly for connecting large peripheral devices, such as printers or scanners to a computer.

Mini-USB (or Mini-B USB): Significantly smaller, the Mini-USB Type-B ports are found in older portable devices, such as digital cameras, smartphones, and older portable drives. This design is now close to obsolete.

Micro-USB (or Micro-B USB): Slightly smaller than Mini-USB, the Micro-USB Type-B port is currently being replaced by USB-C as the charging and data port for latest smartphones and tablets.

Micro-USB 3.0 (or Micro-B USB 3.0): This is the widest design and mostly used for USB 3.0 portable drives. Most of the time, the Type-A end of the cable is blue.

Standard-B USB 3.0: This design is very similar to the Standard-B, however, it's designed to handle USB 3.0 speed. Most of the time, both ends of the cable are blue.

Note that there's also another, less popular, USB 3.0 Powered-B plug and connector. This design has two additional pins to provide extra power to the peripheral device. Also, there's a relatively rare Micro Type-AB port that allows the device to work as either a host or a peripheral device.

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A few proprietary USB cables for Samsung and Apple devices. Dong Ngo/CNET

Proprietary USB

Not all devices use the standard USB cables mentioned above. Instead, some of them use a proprietary design in the place of the Type-B plug and connector. The most famous examples of these devices are the iPhone and the iPad, where either a 30-pin or Lightning connector takes place of the Type-B end. The Type-A end, however, is still the standard size.

USB revisions

Top speed Max power output Power direction Cable configuration Availability
USB 1.1 12Mbps N/A N/A Type-A to Type-B 1998
USB 2.0 480Mbps 5V, 1.8A Host to peripheral Type-A to Type-B 2000
USB 3.0 / USB 3.1 Gen 1 5Gbps 5V, 1.8A Host to peripheral Type-A to Type-B 2008
USB 3.1 / USB 3.1 Gen 2 10Gbps 20V, 5A Bi-directional / Host to peripheral (compatible) Type-C both ends, reversible plug orientation / Type-A to Type-C (compatible) 2013

USB versions

USB 1.1: Released in August 1998, this is the first USB version to be widely adopted (the original version 1.0 never made it into consumer products). It has a top speed of 12Mbps (though in many cases only performs at 1.2Mbps). It's largely obsolete.

USB 2.0: Released in April 2000, it has a max speed of 480Mbps in Hi-Speed mode, or 12Mbps in Full-Speed mode. It currently has the max power out put of 5V, 1.8A and is backward-compatible with USB 1.1.

USB 3.0: Released in November 2008, USB 3.0 has the top speed of 5Gbps in SuperSpeed mode. A USB 3.0 port (and connector) is usually colored blue. USB 3.0 is backward-compatible with USB 2.0 and its port can deliver up to 5V, 1.8A of power. This is sometimes refereed to as USB 3.1 Gen 1.

USB 3.1 (sometimes refereed to as USB 3.1 Gen 2.): Released in July 26, 2013, USB 3.1 doubles the speed of USB 3.0 to 10Gbps (now called SuperSpeed+ or SuperSpeed USB 10 Gbps), making it as fast as the original Thunderbolt standard. USB 3.1 is backward-compatible with USB 3.0 and USB 2.0. USB 3.1 has three power profiles (according to USB Power Delivery Specification), and allows larger devices to draw power from a host: up to 2A at 5V (for a power consumption of up to 10W), and optionally up to 5A at either 12V (60W) or 20V (100W). The first USB 3.1 products are expected to be available in late 2016, and will mostly use USB Type-C design.

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A compatible Type-C USB cable from Aukey that has a Type-A end. Dong Ngo/CNET

USB Type-C (or USB-C)

Physically, the Type-C port and connector is about the same size as that of the Micro-B USB mentioned above. A Type-C port measures just 8.4 by 2.6mm. This means it's small enough to work for even the smallest peripheral devices. With Type-C, a USB cable's both ends are the same, allowing for reversible plug orientation. You also don't need to worry about plugging it in upside down as it will function both ways.

Since 2015, USB-C has been widely adapted and used in many phones and tablets. Many new storage devices also use USB-C port instead of an USB-B port. Almost all devices that support USB 3.1 use the USB-C port. USB 3.1 has the top speed of 10Gbps and can deliver the power output of up to 20V (100W) and 5A. When you consider most 15-inch laptops require just around 60W of power, this means in the future they will be charged the way phones are now, via their little USB port. Apple's new MacBook has just one USB-C port as the sole peripheral and power port.

Type-C USB also allows for bi-directional power, so apart from charging the peripheral device, when applicable, a peripheral device could also charge a host device. All this means you can do away with an array of proprietary power adapters and USB cables, and move to a single robust and tiny solution that works for all devices. Type-C USB will significantly cut down the a amount of wires currently needed to make devices work.

One port, one cable, no fuss

Type-C USB and USB 3.1 are backward-compatible with USB 3.0 and USB 2.0. In a pure Type-C USB connection, the Type-A ports and plugs are no longer included. However, you'll find compatible Type A to Type C cables. On top of that there will be adapters to make Type C hosts and devices work with existing USB devices.

This is the first time adapters are required with USB, and likely the only time, at least for the the foreseeable future. USB Implementers Forum, the group responsible for the development of USB, says that Type-C USB is designed to be future-proof, meaning the design will be used for future and faster USB versions.

It will take a few years more for Type-C become to become as popular as the current Type-A on the host side, but when it does it will simplify the way we work with devices. In fact, Intel is even working on a USB audio standard that might render the 3.5mm audio jack obsolete. And with the addition of Thunderbolt 3 now being the super-set of USB-C, eventually, we'll just have only one type of port and cable to connect all peripheral devices together and to a computer. It's predicted that thanks to the support for USB-C, the adoption of Thunderbolt 3 will take off, which hasn't been the case with previous versions of Thunderbolt.

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