Thunderbolt vs. SuperSpeed USB 3.0

Thunderbolt is slimmer and has transfer rates of 10Gbps, compared with SuperSpeed USB's 5Gbps

Intel will tell you its new high-speed interconnect technology, Thunderbolt, is not in competition with Universal Serial Bus (USB), the ubiquitous standard for connecting computers with other devices.

Apple has gone all in with Thunderbolt-enabled products, and there are a dozen or so manufacturers ready to ship Thunderbolt-enabled systems next year, according to an Intel spokesman. At the Intel Developer Forum in September, a dozen new products were displayed with Thunderbolt ports.

"You can look forward to seeing Windows-based systems with Thunderbolt in market in the first half of 2012," said Intel spokesman Dave Salvator. Microsoft has also already demonstrated Windows 8 support for Thunderbolt.

Thunderbolt, announced earlier this year, offers twice the performance of the latest SuperSpeed USB (3.0) interconnect. So there is reason to believe it could someday overtake USB, the most ubiquitous external I/O technology ever created.

The Thunderbolt port on an Apple MacBook Pro

Salvator said Intel sees Thunderbolt as "complementary" to the USB protocol, which Intel also co-developed, but it is serving the needs of devices with higher performance requirements.

"When Intel comes out with Thunderbolt, a whole ecosystem begins building Thunderbolt stuff," said Steve Duplessie, founder and senior analyst of market research firm ESG.

According to Salvator, Acer and ASUS have publicly stated that their 2012 platforms will have Thunderbolt, but system manufacturers such as Dell, Lenovo and Hewlett-Packard have yet to do the same. All three told Computerworld that they're still "evaluating" the technology.

USB is among the most successful interfaces in the history of personal computers. Among PC and peripheral device manufacturers, USB adoption is virtually 100%. The USB installed base is more than 10 billion units, and those devices are growing at more than 3 billion a year. So it's hard to imagine any external device interconnect technology that could challenge USB.

USB 3.0
A SuperSpeed USB cable

SuperSpeed USB is optimized for power efficiency. It uses only 1.5 amps of power for charging devices, or about one-third of the power of its predecessor Hi-Speed USB (v2.0).

"We also deliver more power for faster charging," said Jeff Ravencraft, president of the USB Implementers Forum (USB-IF), a nonprofit organization founded by the developers of the USB specification, which includes Intel, Microsoft and Hewlett-Packard. "Power is king today, and the way you manage it is pinnacle."

The current Hi-Speed USB (2.0) specification offers external devices up to 500 milliamps for charging. SuperSpeed USB offers up to 900 milliamps, which translates to 4.5 watts, according to Ravencraft.

By the numbers

SuperSpeed USB 3.0 Thunderbolt
Speed 4.8Gbps 10Gbps
Power for devices 4.5 watts 10 watts
Cost $4.49 (for 2-meter cable) $49.00 (for 2-meter cable)
Connector size 11.5mm X 4.5mm 8.3mm X 5.4mm
Downloading 25GB HD movie 60-75 seconds 30 seconds
Source: Intel, USB-IF

If the port is designed to support the USB Battery Charging specification, then the amount of power is upped to 7.5 watts (1.5 amps at 5 volts). Additionally, the USB 3.0 Promoter Group recently announced plans to release a new USB power delivery specification, targeted for completion in early 2012, that would enable higher voltage and current in order to deliver power of up to 7.5 watts over current cables and up to 100 watts over new cables, he added.

Such a thing as too much bandwidth?

On paper, at least, Thunderbolt does beat USB. Thunderbolt offers a 10Gbps transfer rate, compared with SuperSpeed USB's 5Gbps. Thunderbolt is 12 times faster than FireWire 800 and up to 20 times faster than USB 2.0. Thunderbolt can transfer a full-length, high-definition movie in less than 30 seconds. USB SuperSpeed would take about 70 seconds to perform the same task, according to Ravencraft.

Thunderbolt also offers up to 10 watts of power to a device.

USB-IF CTO Rahman Ismail said that while Thunderbolt may offer twice the bandwidth of SuperSpeed USB, most people simply won't need it and, in fact, most applications will still be well served with USB 2.0.

"It's a question of what markets are being satisfied by the bandwidth requirements," Ismail said.

Based on copper, the Thunderbolt specification contains two 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.

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

Intel sees Thunderbolt supporting high-speed storage devices such as RAID arrays, HD displays and PCIe expander boxes for laptops -- pretty much anything that can benefit from a really fast I/O.

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