What is Thunderbolt?

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What Is Thunderbolt?

...And how is it different from other data and video formats?

Thunderbolt is a video and data cable format developed by Intel. It originally employed Apple's Mini DisplayPort connector as a physical format, but with the release of Thunderbolt 3 it now uses a USB Type-C connector in conjunction with a proprietary cable design. Thunderbolt can carry an extraordinary amount of data, and is used both as a single-cable docking solution, and as a high-speed way to access external storage. As a video-out port, it can be converted to DisplayPort, DVI, HDMI, and VGA formats by using an adaptor.

Thunderbolt was developed by Intel, with the intention of creating a consumer-friendly fiber optic format for high speed peripherals. During development, the medium was changed to copper due to the cost of fiber optic components, and concerns about the durability of cables. Copper cables also provide an easy way to supply power, allowing Thunderbolt to compete with other self-powered high-speed formats like USB 3. While Thunderbolt optical cables are available, they actually use a copper connection on the computer and device ends, but convert the signal to optical in the middle, similar to many other long-range extension devices.

How does Thunderbolt work?

Thunderbolt uses the same miniaturized connector as USB Type-C, but with upgraded internal hardware in the computer and external device. This hardware combines PCI Express and DisplayPort signals into a single digital channel. PCI Express is a generic protocol for transmitting data very quickly that nearly all computers are designed to handle, and DisplayPort is a protocol for transmitting high-resolution digital video. Both protocols utilize data packets, and Thunderbolt multiplexes both protocols into one signal that is sent over the cable. Thunderbolt is primarily designed to use twisted pairs of copper wire, despite being initially conceived as a fiber optic format. While Thunderbolt fiber optic cables are available for longer lengths, they actually use a blend of copper and fiber: copper terminals at both ends of the cable and fiber optic wire in the middle. A special chip in each connector converts electric signals to optical signals and vice versa. Intel has stated that their eventual goal is to develop chipset-level support for pure optical cables, increasing efficiency and dramatically lowering costs. Thunderbolt also includes low-voltage DC output for supplying a small amount of power to devices.

What can Thunderbolt do?

Thunderbolt is capable of carrying an incredible amount of data, as well as video and audio. Like DisplayPort and USB, Thunderbolt can be daisy-chained to multiple devices from one port - up to six. Aside from monitors, most Thunderbolt compatible peripherals are external storage devices such as HDDs, SSDs, and RAID arrays. More recently it has appeared on external GPUs, which provide additional graphics processing punch to lightweight systems and laptops. Thunderbolt 3 can reach speeds of up to 40Gbps, while supporting two 4K UHD displays at 60 Hz, and providing up to 100W of power.

Thunderbolt 2

Thunderbolt 2 had similar overall bandwidth capabilities to its predecessor, however it enabled the combination of the two duplex lanes (previously limited to two separate lanes of 10 Gbit/s each) into a single 20 Gbit/s signal capable of simultaneously transferring and streaming 4K video to a monitor. Thunderbolt 2 is backwards compatible with all Thunderbolt peripherals, and includes support for all DisplayPort 1.2 compatible devices.

Thunderbolt 3

Thunderbolt 3 eschews the original Mini DisplayPort connector for a USB Type-C connector, and increases the maximum bandwidth to 40Gbps. It also adds support for a second 4K UHD display at 60 Hz, and increases the amount of available power to 100W. Unlike previous versions, Thunderbolt 3 will function with a standard Type-C cable (as opposed to one specifically made for Thunderbolt), however it will reduce its performance to roughly Thunderbolt 2 levels - a 20 Gbps data rate, and a single 4K monitor. Beware of cables advertised as "Thunderbolt Compatible" if they only advertise a 20 Gbps rate - they're just regular USB Type-C cables.

Thunderbolt vs USB 3.0/3.1

Thunderbolt has an advantage here, in that it supports video as well as data, though USB controls the vast majority of the computer-to-peripheral market, and is generally cheaper and more common than other cable formats. When deciding between the two, the most important factor to consider is whether the additional bandwidth provided by Thunderbolt is necessary for your application.

Thunderbolt vs Firewire 800

Firewire is a cable format developed by Apple for high speed data transfer. While it maintains a small following among some media production professionals, it is slowly being supplanted on the low end by USB, and on the high end by eSATA and Thunderbolt.

Thunderbolt vs DVI

DVI is a video format which is being slowly phased out in lieu of more compact cable formats with a wider range of capabilities, such as DisplayPort, Thunderbolt, and HDMI. It doesn't have any particular advantages over Thunderbolt, but it does exist on a wide range of legacy products.

Thunderbolt vs HDMI

Despite its near-ubiquity, HDMI can be considered only an indirect competitor to Thunderbolt, as they have somewhat different applications. While HDMI is used primarily as a display connector, Thunderbolt is used for both video and data applications. In direct comparison of their video capabilities, HDMI supports a single 4K UHD display at 60 Hz, and Thunderbolt can support two.

Comparison Chart

Speed DC Power Signal Types Max Spec Length
Thunderbolt 10 Gbit/sec x 2 Yes Data, Audio, Video 3 Meters
Thunderbolt 2 20 GBit/sec Yes Data, Audio, Video 3 Meters
Thunderbolt 3 40 GBit/sec Yes Data, Audio, Video 3 Meters
DVI-D Dual-Link 9.12 Gbit/sec No Video 4.5 Meters
HDMI 8.16 Gbit/sec No Audio, Video, Ethernet 5 Meters
FireWire 800 3.2 Gbit/sec Yes Data 4.5 Meters
USB 3.0 5 Gbit/sec Yes Data 3 Meters

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