One big draw for Thunderbolt was that its added bandwidth that allowed both display and data throughput on a single cable.
For example, connecting an external hard drive via a USB 3.1 certified piece of hardware will offer 4.5W of power plus about 10Gbps of data (before overhead). By comparison, Thunderbolt 2 offers 10W of power plus 16Gbps of data (before PCIe overhead).
So, for example, a user could connect a hard drive and a 4K (ultra-high definition) display, which requires from 12-14Gbps, according to according to Ben Hacker, the planning and operations manager with Intel's Client Connectivity Division.
Intel is also adding peer-to-peer computer networking capabilities to Thunderbolt 2. The new feature will allow Macs and eventually PCs to connect directly for high-speed data transfers.
The new, symmetrical Type-C USB Connector (top) compared with the USB 3.1 Connector (bottom).
So why has Thunderbolt failed to catch on? One word: Cost.
Thunderbolt transmitters/receivers cost more, according to O'Rourke. And, they're not integrated into CPUs in PCs; they're discrete chips that must be added onto a PC board, or the board on any PC peripheral.
"In addition, there may be some royalty costs, but I'm not certain about this," O'Rourke said.
The Thunderbolt specification is a combination of two connectivity protocols: PCI Express (PCIe) and DisplayPort. The Thunderbolt chip switches between the two protocols to support varying devices. DisplayPort offers HD display support as well as eight channels of HD audio. A Thunderbolt connector has two full-duplex channels; each are bi-directional and capable of 10Gbps of throughput.
Intel invented both USB and Thunderbolt, and the company continues to maintain that they're "complementary" not competitive technologies.
But the differences between the two specs are becoming less obvious.
Other than throughput, one of Thunderbolt's attributes that gave it a leg up over USB was that peripheral hardware could be daisy chained through it. That means multiple displays, hard drives, or other even other computers can be connected to a single Thunderbolt port.
Ravencraft scoffed at the idea that the ability to daisy chain peripherals together sets Thunderbolt apart. "This whole daisy chain thing, in our world we just call it a hub," he said, reiterating that the additional bandwidth of USB SuperSpeed+ will allow more peripherals to be connected to the same port.
Thunderbolt 2's 2X throughput over even USB 3.1 will still be a big attractor, Hacker said.
"I think the big draw here is getting data and display [I/O] on the same pipe," Hacker said. "The applications that require 20Gbps are limited, but the most interesting applications of [Thunderbolt] are really around combining the bits needed for data, and also the bits needed for display onto a single simple interface.
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