Sequel to Thunderbolt is all about 4K video

The next generation of Intel's Thunderbolt interface was officially given a name yesterday. Formerly referred to by its controller's code name, "Falcon Ridge," Intel has announced that the latest iteration will be called "Thunderbolt 2." It's not terribly creative, but it does stick with the existing branding.

We've talked about Intel's sequel to Thunderbolt before. The technology (originally marketed as an optical-only interface under the codename "Light Peak") has become one of the standard ports on current-generation Apple computers, but it's been much slower to appear on the PC side of the aisle. We've speculated before that this is likely due to licensing issues more than anything else; regardless of the cause, Intel is hoping that the "widespread adoption of 4K video technologies" will in turn drive more folks to the high-bandwidth bus.

That, in fact, is Intel's overriding message. Intel's announcement blog post focuses heavily on the creation and consumption of 4K video, almost to the exclusion of everything else. To that end, Thunderbolt 2 doesn't include an increase in the total throughput the connection can provide, but it does aggregate the data channels together. Rather than four 10Gbps lanes spread across two channels, Thunderbolt 2 provides two 20Gbps lanes across one channel. This gives the bus the necessary throughput to push the required 3840×2160 pixels while maintaining headroom for other applications to also use the bus.

To actually let 4K displays take advantage of the increased per-lane bandwidth, Thunderbolt 2 supports DisplayPort 1.2. Intel also points out that the cabling and connectors will remain the same with Thunderbolt 2, and that Thunderbolt 2-equipped computers and devices will be fully backward-compatible with existing Thunderbolt devices.

The mechanism behind this backward compatibility isn't fully explained in Intel's blog post, but it's almost certain that Thunderbolt 2's 20Gbps channels can be split to provide for older devices, with 10Gbps streams either multiplexed by the controller into 20Gbps streams, or with the entire bus simply falling back to Thunderbolt 1. It's also unclear how mixed Thunderbolt 2 and Thunderbolt 1 devices would behave on the same bus, and if there are guidelines for how and in what order mixed devices should be connected.

On availability, Intel says that Thunderbolt 2 "is currently slated to begin production before the end of this year and ramp into 2014." The "before the end of the year" time frame means that Thunderbolt 2 will be supported on Haswell chipsets rather than waiting for the appearance of Broadwell (the die-shrink "tick" to Haswell's new microarchitecture "tock"), since according to Intel's roadmap, Broadwell CPUs aren't expected to show up before mid-2014.