Three-Minute Tech: Thunderbolt


For about a year, Macs have been shipping with a fancy new port on the side called Thunderbolt. We're just on the cusp of seeing this new port on Windows-based PCs, too. What exactly is Thunderbolt, and should you make sure your next computer has it?

Thunderbolt is fast

Thunderbolt is a method for transferring data between devices, much like USB or FireWire. The key difference is that it’s much faster. For example, the current USB 3.0 standard maxes out at 5gbps (gigabits per second). Thunderbolt gives you up to two channels that each transfer data at 10gbps.

Thunderbolt was co-developed by Intel and Apple. It was originally meant to be an optical interface, connecting devices via fiber optic cable. Improvements in signaling technology over copper wires allowed the Thunderbolt to be implemented purely on copper wire, which helps make it less expensive to build into PCs and also gives it the ability to supply power to externally attached hardware.

DisplayPort + PCIe

At its core, Thunderbolt actually melds two different standards: DisplayPort and PCI Express. DisplayPort is the latest standard for connecting monitors to PCs and Macs, and is slated to replace the aging DVI standard. PCI Express is a point-to-point I/O standard designed to move data at high speeds. PCIe, as it’s often referred to, can move data bidirectionally—both sending and receiving data at the same time.

Thunderbolt multiplexes both DisplayPort and PCI Express signals into a single stream, then splits the correct stream out at the destination. [Source: Intel]

This combination has some key benefits. First, existing connectors can be used. Thunderbolt uses the mini-DisplayPort connector originally developed by Apple and now available across a variety of systems and peripherals. Second, devices can be daisy-chained. You can have one Thunderbolt cable going from your computer to an external hard drive, and then another cable going from that hard drive to a monitor, for example. The one exception are older monitors that support only the DisplayPort 1.1 spec, rather than the more current DisplayPort 1.2. Those displays must be attached only at the end of the chain. Daisy-chaining devices reduces cable clutter, and minimizes the need for add-on hubs to increase connections.

Today’s systems use a discrete Thunderbolt controller chip to handle the needed multiplexing (combining) of the DisplayPort and PCIe signals into a single data stream. Current Thunderbolt cables are active cables which are “smart”; they have controller chips embedded in the connectors to help manage traffic.

Current implementations use discrete Thunderbolt controller chips directly connected to PCI Express and DisplayPort on the system side. [Source: Intel]

Thunderbolt's future

Thunderbolt interfaces originally appeared on Apple’s MacBook and iMac line of computers, but Windows-based systems with Thunderbolt built in are just starting to appear. Thunderbolt and USB will continue to coexist, as they serve slightly different needs. Thunderbolt can deliver the high data rates needed for displays or large storage systems, while USB is better suited for small peripheral connections, like keyboards and mice.

While today’s Thunderbolt standard uses copper wire, Intel is still working on developing Thunderbolt over optical cable. That could result in even higher data speeds. Perhaps more useful, cables could be much longer, allowing more flexible placement of storage systems or large, multi-monitor video walls with minimal cabling needs.

Do you need to make sure your next computer has a Thunderbolt port? Thunderbolt is still in its infancy, but new peripherals—particularly storage hardware—are arriving at a rapid clip. Users who need a lot of high speed storage, like video editors and photographers—will want Thunderbolt. It's not as useful for everyday mobile storage, even though it's faster than USB 3.0, because smaller devices tend to be somewhat slow unless those small external drives house a fast SSD.

Until we see widespread adoption of DisplayPort 1.2 in monitors, Thunderbolt won't be as useful on the PC side as it is on the Mac side. Monitors with DisplayPort 1.2 will start to arrive by the end of summer, 2012.

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