USB SuperSpeed will relegate Thunderbolt to a niche

The new technology is expected to eventually scale throughput beyond 40Gbps

The USB SuperSpeed specification and accompanying hardware are about to undergo a number of major evolutionary makeovers that will leave little room for the Thunderbolt hardware interface to expand in the market.

Both USB SuperSpeed and Thunderbolt have recently undergone version upgrades - USB moved to v3.1 (SuperSpeed+) and Thunderbolt to v2. And both upgrades double the maximum throughput speed -- USB 3.1 to 10Gbps and Thunderbolt 2 to 20Gbps.

But, the USB SuperSpeed specification has a lot of elasticity built into it.

"This tech will scale well beyond 10Gbps," said Rahman Ismail, a USB 3.0 senior architect at Intel. "We believe we already have a protocol that will scale well past 40Gbps."

Other than speed, Thunderbolt 2 has another advantage over USB 3.1 - 10 watts of power compared with USB SuperSpeed's 4.5 watts.

PCI Express and DisplayPort are transported between Thunderbolt controllers over a Thunderbolt cable (Source: Intel Corp.)

But, the USB connector specification is also getting long-awaited improvements that will give users a reversible plug orientation and the opportunity for a more robust cable offering up to 100 watts of power. Again, like Thunderbolt, the new USB Type-C Connector means both the cable and the connector plug are symmetrical and the technology will eventually offer 10 times the power of Thunderbolt 2.

The new USB Type-C Connector specification is expected to be completed in July. A more robust version of the cables, capable of supporting 100 watts of power, are expected later next year.

A USB SuperSpeed+ cable certified for 100 watt power transfer could support an external hard drive and an Ultra-High Definition (UHD) 4K television display, according to Jeff Ravencraft, president of the USB Implementers Forum (USB-IF).

USB SuperSpeed 3.1 products are expected to hit the market in early 2015 -- possibly as early as this Christmas, Ravencraft said.

"It's revolutionary. It's like what happened with the phone, when companies standardized on the Micro USB port for charging for consumers.... They no longer had to have custom fit a cable for every phone they bought," Ravencraft said.

Apple continues to be the leading adopter of Thunderbolt connector technology for its desktop and laptops, but it offers it right alongside USB. Beginning last year, HP also adopted Thunderbolt alongside USB 3.0 for a half dozen workstations, but it has yet to add it to any consumer devices.

Brian O'Rourke, a principal analyst covering wired interfaces at IHS, said Thunderbolt's future really depends on its biggest supporter: Apple.

"If they continue to support it, it will survive," O'Rourke said. "USB's installed base is in the billions. Thunderbolt's biggest problem is a relatively small installed base, in the tens of millions. Adding a higher data throughput, and a more expensive option, is unlikely to change that."

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.

For now, Intel seems content with offering Thunderbolt as a "premium" technology.

"I think our expectation of adoption would always be that it would be limited compared to USB," Hacker said. "And that's fine. We, of course, like to see new powerful technology that can really enhance user experiences, but I don't think everyone needs what [Thunderbolt] offers, so perhaps some less than 100% adoption is reasonable."

Lucas Mearian covers consumer data storage, consumerization of IT, mobile device management, renewable energy, telematics/car tech and entertainment tech for Computerworld. Follow Lucas on Twitter at @lucasmearian or subscribe to Lucas's RSS feed. His e-mail address is lmearian@computerworld.com.

See more by Lucas Mearian on Computerworld.com.

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