Intel Talks Thunderbolt 3

One cable to rule them all, and it’ll be optical in 2016

4 min read
Photo-illustration: Intel
Photo-illustration: Intel

Intel is gearing up for what it sees as the biggest revolution since the introduction of USB. In June, the company finalized the development of Thunderbolt 3, a new chip, protocol, and physical connection that Intel hopes will replace all the existing cables we use to connect peripheral devices and allow us to go beyond with some new applications.

Shortly thereafter, we had a chance to sit down with Shahaf Kieselstein, Intel’s general manager for the client connectivity division (and vice president of the client computing group), who headed the development of Thunderbolt 3.

Thunderbolt has been in development at Intel Labs for more than five years and has its origins in the Light Peak project, which was developed by Intel with Apple. As the project moved from the lab to the market, the initial optical fiber of Light Peak gave way to the more traditional copper wiring in the first-generation Thunderbolt, which hit the market back in 2011.

According to Kieselstein, the vision behind Thunderbolt 3 was to create one cable that allows users to connect every type of peripheral to their computers, and to do so with as much bandwidth but as little cabling as possible. More specifically, what the company was trying to do with Thunderbolt 3 was to develop a high speed I/O over a single wire for users who create 4K video content, make it as power efficient as a USB, and keep product cost low enough for use with a client platform such as a laptop (as opposed to a server). Kieselstein wasn’t willing to go into the specifics of the “secret sauce” that allowed Intel to achieve these goals, but he was willing to talk about the amount of effort: two years of work by a relatively small team of about 100 developers.

While USB does a very good job for many types of peripherals, devices such as displays are limited in their functionality, both in terms of resolution and latency, when connected through a USB. In fact, over the past decade or so, most displays have been using either HDMI or DisplayPort in order to reach higher and higher resolutions and faster refresh rates.

While USB, HDMI, and DisplayPort all play a part in today’s digital ecosystem, the lack of a single standard for data and video has forced manufacturers to equip new devices with multiple types of connectors. This takes up space, increases costs, compels users to connect more cables, and in some cases, to use adapters. With Thunderbolt 3, Intel is looking to make all these issues go away while allowing some new and exciting functions that were not possible until now.

For example, Thunderbolt 3 has a 40-gigabit-per-second bus that’s four times as fast as the new USB 3.1 and twice as fast as the previous generation of Thunderbolt. What can you do with so much bandwidth? Well, for starters, you can run two 4K 60-hertz monitors at the same time using Thunderbolt’s built-in support for the DisplayPort 1.2 protocol. (Interestingly, Intel did not include support for the newer DisplayPort 1.3, which can support 4K 3-D—and to some degree even future 8K resolutions—with a single cable, but Kieselstein did not say why.)

You also have four lanes of support for the computer expansion bus PCI Express Gen 3 built in. This allows users to connect practically any internal PCI Express card externally, leading to some interesting use scenarios. One of the most exciting, according to Kieselstein, is connecting a graphics dock to a thin, light mobile computer—essentially bringing desktop-level performance to small laptops. Intel already partnered with AMD (and Nvidia might join in the future) to create two types of docks: a Thunderbolt graphics dock for a mobile graphics unit (which is what we were shown driving two 4K 60-Hz displays when we visited Intel) and a much larger Thunderbolt card chassis, which will house a full desktop GPU for heavy-duty games and other graphics-intensive tasks.

Having fast external PCI Express support allows another interesting feature that Intel demonstrated: ultrafast external storage. By using NVM Express—a specification for attaching solid-state drives to PCI Express—users will be able to connect these new drives to any device (including future Thunderbolt 3–supported laptops) with up to four times the transfer speed of the fastest SATA drives around.

Both the external storage and graphics applications of Thunderbolt 3 point to a more general trend, which Intel emphasized in our conversation—smart docking stations. Thunderbolt 3 docking stations, which will likely be among the first consumer devices to reach the market, will show off yet another of the protocol’s benefits: enhanced power delivery.

Using a Thunderbolt 3 cable with a docking station connected to AC power, a laptop can have a fast data connection through USB 3.1, connect PCI Express devices externally, and drive ultrahigh-resolution monitors using dual DisplayPort 1.2. In addition, the setup can charge the laptop (at up to 100 watts), as well as supply up to 15 watts to external devices that don’t have their own power sources. (That’s up from about 10 W in Thunderbolt 2.)

Previous iterations of the Thunderbolt were costly because they required an “active” cable, which has a chip in it to boost performance. The move to a USB Type-C connector, plus the ability of Thunderbolt 3 to work with both fast, active cables (40 Gb/s) and less-expensive, passive cables (up to 20 Gb/s), means that cost will be less of an issue this time around.

An optical version of Thunderbolt 3, which will extend its reach to 60 meters from today’s 2 meters, is expected to arrive in mid-2016.

On top of graphics, storage, power, and USB, Thunderbolt 3 will also offer the ability to daisy-chain up to six devices as well as to emulate a 10-gigabit Ethernet connection. That latter capability will let users connect two Thunderbolt 3–supported computers directly in order to transfer large amounts of data quickly.

At the moment, the Thunderbolt 3 chip, known as Alpine Ridge, isn’t part of Intel’s CPU. But Kieselstein says that given enough demand for its native USB 3.1 host controller and the enhanced storage, graphics, power, and data transfer capabilities it provides, adding Thunderbolt directly to a computer’s system-on-a-chip will be possible. (The chip, by the way, is manufactured by foundry giant and sometime Intel rival TSMC.)  

For desktop computers lacking Alpine Ridge, Kieselstein says that Intel is developing an add-on PCI Express card with Thunderbolt 3 support, just as it did with previous versions of Thunderbolt.

The first Thunderbolt 3–enabled products (mostly laptop computers featuring Alpine Ridge chipsets) are already here, but, according to Intel, the full range of products based on the new technology—including the aforementioned connectors and docking stations—will hit the market after the new year.

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