Thunderbolt vs. SuperSpeed USB 3.0

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Intel Thunderbolt interconnect technology
Intel Thunderbolt interconnect technology
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.

Is Thunderbolt "Complementary?"

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.

Power Efficiency

Superspeed USB
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.

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.

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.

Salvator pointed to Thunderbolt-enabled products shown at the IDF conference earlier this month that included high-speed storage devices (RAID arrays), HD media capture, displays and a PCIe expander for laptops. He also said Intel will continue supporting its other interconnect technology.

Thunderbolt Only on Apple Products, So Far

Apple MacBook Air
Apple MacBook Air
To date, Apple is the only company selling computers with Thunderbolt ports. Sony may be planning to ship a laptop this year with a Thunderbolt port. Intel is designing two new, lower-cost Thunderbolt controllers for developers designing systems around its Ivy Bridge chip.

Apple was the first to add Thunderbolt ports in conjunction with USB ports on its MacBook Air, MacBook Pro, iMac and Mac mini, offering customers access to high-resolution displays greater than 1080p.

Apple pitches its new 27-in. Thunderbolt display as the way to turn a MacBook Air into a workstation. The Thunderbolt port not only powers the display's 2560x1440 resolution, but allows daisy-chaining of peripherals. This means that as many as five peripherals can be added to the Apple Thunderbolt Display, including a Promise Pegasus RAID array or a LaCie Little Big Disk, the first Thunderbolt-enabled external hard drive.

"You can see that it provides a lot of I/O versatility integrated into the display," Salvator said.

What products are shipping?

Unlike Apple and Sony, not all device manufacturers are interested in supporting Thunderbolt on their systems. Earlier this year, HP considered using Thunderbolt in its PCs, but then said it would stick with USB 3.0.

Thunderbolt's Price Premium

Other manufacturers will likely follow suit. Because it is new, Thunderbolt carries a heavy price premium. For example, a Hi-Speed USB (2.0) cable sells for about $1.50, and the chipset sells for less than $1, according to Ismail. A SuperSpeed cable brings a price premium, but it still sells for only about $4.49

In contrast, a Thunderbolt cable sells for $49. Intel's Salvator did not offer pricing for the Thunderbolt controller; however, Intel plans to offer a lower-cost chipset, dubbed Cactus Ranch, next year.

"You've got to sell 45 USB cables to make the same money as you would with one Thunderbolt cable. It's the same wire and manufacturing cost. At the beginning of a tech cycle, it's just pure profit, effectively," Duplessie said. "Let's face it. USB is probably not going to stop. For 99% of the world, USB 2.0 is probably fast enough, let alone USB 3.0."

But "it's still early days," said David Johnson, an analyst for desktop and mobile infrastructure and operations at Forrester Research.

Johnson said the ubiquity of USB devices will be an enormous factor in future adoption of Thunderbolt by system manufacturers and consumers, but the interconnect is also slimmer than USB, making it ideal for netbooks, tablets and any thin computer technology.

For example, Intel is releasing a new category of ultra-thin notebooks this holiday season called Ultrabook. And while the company is not requiring that equipment manufacturers use Thunderbolt on those computers, it's a good bet that many will, Johnson said.

"That's a good form factor to drive Thunderbolt," Johnson said.

Like Thunderbolt, USB 3.0 is also in its early days. The majority of products are only shipping in peripheral devices, which include flash memory sticks and external hard drives.

However, PC manufacturer Asus shipped 2 million USB 3.0 motherboards to system manufacturers in the first quarter of this year. Semiconductor maker Renesas Electronics announced that 30 million USB 3.0 host controllers shipped through May 2011, and motherboard maker Giga-Byte Technology is on track to ship 7.5 million USB 3.0 motherboards by the end of this year.

Certified USB 3.0 host controllers are available from seven other companies, including Advanced Micro Devices, ASMedia, and Etron. AMD announced its first certified SuperSpeed USB chipset at IDF Beijing 2011. Intel announced support for USB 3.0 integration into its Ivy Bridge chipset at its developer forum earlier this month.

In the end, though, it will be up to the consumer to show vendors through their purchases if they want the added bandwidth and power that Thunderbolt offers.

"If you have two machines and one has Thunderbolt and one does not, and the cost is not a big differentiator, then certainly someone who chooses the one with the Thunderbolt port will open up more possibilities," Johnson said.

This story, "Thunderbolt vs. SuperSpeed USB 3.0" was originally published by Computerworld.

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