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What is Thunderbolt High Speed I/O?


Thunderbolt High Speed I/O - What is Thunderbolt High Speed I/O?
Thunderbolt High Speed I/O - What is Thunderbolt High Speed I/O?

Question: What is Thunderbolt High Speed I/O?

I've read that Apple now includes Thunderbolt high speed I/O in its latest Macs. What exactly is Thunderbolt, and how can I make use of it?


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

Thunderbolt was originally 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 blazingly 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 substantially increase the cost. 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.

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.

  • USB 2.0: 480 Mbps
  • USB 3.0: 4.8 Gbps
  • FireWire 800: 786 Mbps
  • FireWire 1600 (not yet available): 1.6 Gbps
  • FireWire 3200 (not yet available): 3.2 Gbps
  • SATA II: 3 Gbps
  • SATA III: 6 Gbps
  • Thunderbolt: 10 Gbps per channel

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.

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 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

As of early 2011, there are no native Thunderbolt-enabled peripherals that can 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.

Third-party devices should be available by mid summer. Apple and Intel both expect a range of devices, including displays, storage devices, audio/video devices, cameras, docking stations, and device converters for plugging USB or FireWire devices into a Thunderbolt cable.


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