How fast are the MacBook's USB 3.0 and Thunderbolt ports?
- 13 June, 2012 18:41
With the launch of the new MacBook Air and MacBook Pro this week, Apple became the only laptop manufacturer to offer both a high-speed Thunderbolt port and two USB 3.0 (USB SuperSpeed) ports for external peripherals.
By upgrading from the USB 2.0 standard to 3.0, the laptops offer 10 times the I/O bandwidth for external devices. That translates into markedly faster backups to external storage devices.
The Thunderbolt protocol offers even greater performance. On paper, 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 Jeff Ravencraft, president of the USB Implementers Forum (USB-IF).
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.
Thunderbolt also offers up to 10 watts of power to a device. 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).
Thunderbolt has the ability to serve as a transport for PCI Express (PCIe), something USB is incapable of. PCIe is a computer expansion bus standard, the main advantage being users who've already invested in PCIe-enabled devices can continue to use them.
One major drawback to Thunderbolt is the high cost of hardware because it is still a fairly new technology. For example, a USB SuperSpeed cable sells for around $3. A Hi-Speed USB (2.0) cable sells for about $1.50, and the chipset sells for less than $1, according to USB-IF Chief Technology Officer Rahman Ismail.
By the numbers
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. It's hard to imagine any external device interconnect technology that could challenge USB.
Jeff Cable, an official photographer for the USA Water Polo Team, who has covered three Olympics games, said the MacBook Pro's upgraded ports and retina display will make it the perfect machine for him.
"Not only with the processing power, the SSD, the amazing screen, but with the addition of USB 3.0 for fast downloading (using the Lexar Pro USB 3.0 reader) and two Thunderbolt ports for connecting [external storage]," he said. "I can't ask for a better tool."
Cable said having an internal SSD, as the MacBook Air and MacBook Pro now offer, is great for the speed, but it also highlights the need for a high-capacity, high-speed external device. "Shooting more than 100GB a day, a 512GB SSD won't last long," he said.
Forrester analyst David Johnson said Thunderbolt and USB 3.0 offer significant I/O performance boosts, but their real value will be seen when external solid-state drives (SSDs) hit the market.
"SSD performance potential will exceed what USB 3.0 can really leverage. There is one external SSD drive on the market now, but I'm looking forward to more because then it will allow me to meaningfully expand the capacity of high performance storage I can take with me on the road," Johnson said.
Computerworld tested the industry's first Thunderbolt-equipped external SSD backup drive, the Elgato Thunderbolt SSD, with a Thunderbolt-enabled MacBook Pro. The results were impressive.
Using a MacBook Pro equipped with a USB 2.0 port and a top-of-the-line thumb drive from Imation, Computerworld was able to transfer a 1.19GB file with 327 JPG images in 1 minute, 4 seconds. Using the Thunderbolt port and the Thunderbolt SSD, the transfer time for the same file was cut in half to 33 seconds.
A Time Machine backup to the Thunderbolt drive, which entailed copying 11.1GB of data and more than 300,000 files, took just 15 minutes, 35 seconds. By comparison, a Time Machine backup using an external hard disk drive and USB 2.0 took 48 minutes.
Johnson said there are several laptop models that have USB 3.0, and Lenovo, Asus and Acer have announced plans for Thunderbolt support, but the MacBook Pro and MacBook Air are the only computers with both ports, giving Apple a leg-up on competition.
The Acer Aspire Ethos, HP Spectre and the Dell XPS13 offer USB 3.0 ports. "The HP and Dell also have switched to the Mini Displayport standard, which looks like a Thunderbolt port but isn't," Johnson said.
One major advantage Thunderbolt has over USB 3.0 is its ability to daisy-chain 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.
Because of the ability to daisy chain, one big selling point is that the user would only need one port, versus multiple ports for all Thunderbolt-enabled peripherals, including USB peripherals, into a Thunderbolt-equipped monitor.
Johnson pointed out that daisy-chaining offers users a cleaner desk with fewer cables, a cheaper alternative to a docking station, and a computer with a cleaner design.
"I've been using Thunderbolt for several months now with a MacBook Air coupled to an Apple Thunderbolt display and a Firewire 800 drive daisy-chained to the display. Thunderbolt has proven extremely stable for me and the Firewire 800 drive I have is very fast. The best way to describe it is in what it allows me to do with massive files like video projects and virtual machines," Johnson said.
Previously, it was not practical for Johnson to house a Windows virtual machine in VMware Fusion on an external USB 2.0 drive because it was "dog slow with USB 2.0 as the bottleneck," he said.
"With the Firewire 800 drive and the Thunderbolt display, the performance within the virtual machine is very good. It's not as fast as it is running natively on the SSD storage within the Mac, but it's quite usable," he added.
Lucas Mearian covers storage, disaster recovery and business continuity, financial services infrastructure and health care IT for Computerworld. Follow Lucas on Twitter at @lucasmearian or subscribe to Lucas's RSS feed. His e-mail address is firstname.lastname@example.org.
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