Introduction to Thunderbolt High-Speed I/O

How fast really is it?

With the introduction of new MacBook Pros in early 2011, Apple became the first manufacturer to use Intel's Thunderbolt technology, which provides high-speed data and video connection for computing devices.

Lighting over city
Daniti Delimont/Getty Images

Thunderbolt was initially called Light Peak because Intel intended the technology to use fiber optics; hence the reference to light in the name. Light Peak was to serve as an optical interconnection that would allow computers to send data at blazing fast speeds. It would be used both internally and as an external data port. As Intel developed the technology, it became evident that relying on fiber optics for the interconnection was going to increase the cost substantially. In a move that both cut costs and brought the technology to market faster, Intel produced a version of Light Peak that can run on copper cabling. The new implementation also got a new name: Thunderbolt.

Cable Thunderbolt
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Thunderbolt runs at 10 Gbps bi-directionally per channel and supports two channels in its initial specification. This means that Thunderbolt can send and receive data simultaneously at the 10 Gbps rate for each channel, which makes Thunderbolt one of the fastest data ports available for consumer devices. To compare, current data interchange technology supports the following data rates.

Interface Speed Notes
USB 2 480 Mbps  
USB 3 5 Gbps  
USB 3.1 Gen 2 10 Gbps  
Firewire 400 400 Mbps  
Firewire 800 800 Mbps  
Firewire 1600 1.6 Gbps Not used by Apple
Firewire 3200 3.2 Gbps Not used by Apple
SATA 1 1.5 Gbps  
SATA 2 3 Gbps  
SATA 3 6 Gbps  
Thunderbolt 1 10 Gbps per channel
Thunderbolt 2 20 Gbps per channel
Thunderbolt 3 40 Gbps per channel. uses USB-C connector
Popular Peripheral Interfaces

As you can see, Thunderbolt is already twice as fast as USB 3, and it's far more versatile.

DisplayPort and Thunderbolt

Thunderbolt supports two different communications protocols: PCI Express for data transfer and DisplayPort for video information. The two protocols can be used simultaneously on a single Thunderbolt cable. This allows Apple to use the Thunderbolt port to drive a monitor with a DisplayPort or Mini DisplayPort connection, as well as connect to external peripherals, such as hard drives.

Apple Thunderbolt Display
Apple, Inc.

Thunderbolt Daisy Chain

Thunderbolt technology uses a daisy chain to interconnect a total of six devices. For now, this has a practical limitation. If you're going to use Thunderbolt to drive a display, it must be the last device on the chain, since current DisplayPort monitors don't have Thunderbolt daisy chain ports.

Thunderbolt Cable Length

Thunderbolt supports wired cables up to 3 meters in length per daisy chain segment. Optical cables can be up to tens of meters in length. The original Light Peak spec called for optical cables up to 100 meters. The Thunderbolt specs support both copper and optical connections, but the optical cabling hasn't been made available yet.

Thunderbolt Optical Cable

The Thunderbolt port supports connections using either wired (copper) or optical cabling. Unlike other dual-role connectors, the Thunderbolt port doesn't have built-in optical elements. Instead, Intel intends to create optical cables that have the optical transceiver built into the end of each cable.

Thunderbolt cables
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Thunderbolt Power Options

The Thunderbolt port can provide up to 10 watts of power over Thunderbolt cables. Some external devices can, therefore, be bus-powered, in the same way, that some external devices today are USB powered.

Thunderbolt-Enabled Peripherals

When first released in 2011, there were no peripherals with built-in support for Thunderbolt to connect to a Mac's Thunderbolt port. Apple provides a Thunderbolt to Mini DisplayPort cable and has adapters available for using Thunderbolt with DVI and VGA displays as well as a Firewire 800 adapter.

Third-party devices started making their appearance in 2012 and currently, there is a wide range of peripherals to pick from including displays, storage systems, docking stations, audio/video devices and much more.

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