What Is Apple's Thunderbolt Port?

What Is Apple's Thunderbolt Port?
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The Basics of Thunderbolt

It’s not often that a new I/O port is released, but Apple has always gone its own way when it comes to connectivity, so it’s no surprise that Apple decided to adopt this technology so early.

But what is the Thunderbolt port, exactly? What are is advantages and disadvantages? And how does it work?

Climbing Down Light Peak

Intel has been working on a new connectivity option, code named Light Peak, for the last few years. The name of the project offers a peek into the technology behind it. Intel’s idea was to take advantage of fiber-optic technology, which offers far higher data transfer speeds than a technology based on a metal wire.

However, bringing fiber optics to peripherals is easier said than done. Fiber optics is an expensive technology to implement, and the cables do not as flexible as those based on metal. That’s a practical limitation that isn’t easy to defeat, but it seemed the only way to meet Intel’s goal - a connection capable of data transfers up to 10 Gbps.

Alas, research doesn’t always work how you’d expect. Although Intel researched fiber optics extensively, they managed to achieve their goal using copper wire instead. Since this is much less expensive, Intel decided to move ahead with the more conventional copper wire, and thus Light Peak was smote with the Thunderbolt nameplate.

An Overview of Thunderbolt

Thunderbolt Port

The Thunderbolt connection is new, but the connector itself isn’t. Intel and Apple decided that they could fold Thunderbolt into the existing Mini DisplayPort connection.

Although this seems counter-intutive at first, it should prove beneficial in the long term. Thunderbolt will be able to serve as not only a data connection but also a display connection. In addition, Thunderbolt supports daisy-chain configurations. This means you can extended a single Thunderbolt connection to multiple devices, including both display and storage devices. The benefits of this will be most apparent on mobile computers, which often have limited space for connection options.

Thunderbolt can also serve as an extension of the PCIe bus. This means that expansion cards that normally need to be connected directly to the system board could theoretically be connected to a system via Thunderbolt. This could make external video cards practical, for example. It remains to be seen how this potential pans out, but it’s exciting to see a technology offer such a wide variety of features and outstanding transfer speeds.


Now let’s find out how Thunderbolt compares to other I/O technology.

Firewire - Thunderbolt could be considered a spiritual successor to Firewire. Currently the fastest version of Firewire commonly offered is Firewire 800, which tops out at 800 Mbps. Although Firewire isn’t “dead” yet, Apple has clearly abandoned it in favor of Thunderbolt. This means Firewire is likely on its way out.

USB 3.0 - USB 3.0 offers transfer speeds of up to 5 Gbps before protocol overhead is considered. USB 3.0 is only a data connection, and there are no plans to extend it beyond that. Although quick, common and easy to use, USB 3.0 is at a clear disadvantage to Thunderbolt.

eSATA - This uncommon connection can offer full SATA speeds of up to 3 Gbps or 6 Gbps depending on the connection supported. There is less protocol overhead with eSATA than with USB, so actual transfer speeds are much closer to those quoted. This means SATA 6 Gbps should generally beat the pants off USB 3.0. However, eSATA is very limited in its adoption.


It’s hard to say if Thunderbolt will eventually serve to displace all of these alternatives. Although transfer speed is important, the cost of the connection is also important. If Thunderbolt is expensive, USB 3.0 will likely remain a dominate force. If the price of Thunderbolt is equal or close to USB 3.0, however, then we’ll likely see Thunderbolt take over the market within the next five years.


Intel: Thunderbolt Technology

All images taken from Intel and Apple press materials.