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How fast is USB 3.0 really?

James Galbraith | May 27, 2013
Now that USB 3.0 is found on (almost) every new Mac, the Macworld Lab decided to put its real-world speed to the test, especially compared with FireWire 800 and Thunderbolt.

USB port

As a Mac user, I've never been a big fan of USB for storage. Keyboards, mice, sure. But a hard drive connected via USB has always been slow compared to those using Apple's FireWire, FireWire 800, and (most recently) Thunderbolt interfaces. And booting from a USB drive on the Mac was a no-no for a long time.

Times have changed, however. And thanks to USB 3.0's availability on almost all shipping Macs (and, in the case of the Mac Pro, something you can add via a PCI card), its bootability (since late 2005--but what can I say, I can hold a grudge), its improved performance, and its relatively low price, my bias is quickly disappearing. (Though the first certified USB 3.0 consumer devices were announced at the Consumer Electronics Show in 2010, Macs didn't begin shipping with USB 3.0 ports until June 2012, when new MacBook Air and MacBook Pro models were released.)

USB 3.0 (also known as SuperSpeed USB) has a maximum bandwidth rate of 5 gbps (gigabits per second). That translates to 640 MBps (megabytes per second)--ten times faster than USB 2.0 (aka Hi-Speed USB).

By comparison, Intel's Thunderbolt technology allows theoretical data-transfer speeds of up to 10 gbps on each of its bi-directional channels. On paper, that's twice as fast as USB 3.0, but how fast is Thunderbolt really? Also, you'll currently you pay quite a premium for Thunderbolt (often an extra $100 or more for a drive of the same capacity) and USB 3.0 ports offer backward compatibility with USB 2.0 devices.

We wanted to see if USB 3.0 lives up to its hype, and if Thunderbolt is in fact a faster alternative. So we ran a slew of tests using both spinning and solid-state drives that had a variety of interfaces and were plugged in both directly to a computer and through a USB 3.0 hub. To give the tests the best chance of success, we connected the USB 3.0 drives to a 2012 15-inch MacBook Pro with a 2.7GHz quad-core Intel Core i7 processor, 8GB of RAM, and a speedy internal SSD drive installed. We also tested USB 2.0 and FireWire 800 speeds for comparison.

Hard-drive tests
For our first test, we used a bus-powered, 2.5-inch Hitachi 750GB, 7200-rpm hard drive and ran a series of tests with it connected over USB 2.0 and USB 3.0 directly to our MacBook Pro. We ran the same tests again, but with the USB drive attached to each of two hubs. (We used StarTech's $61 6 Port USB 3.0 / USB 2.0 Combo Hub with 2A Charging Port with two USB 3.0 ports, four USB 2.0 ports, and a seventh USB port used for charging devices; and Belkin's $50 SuperSpeed USB 3.0 4-Port Hub.) We then ran the tests with the drive connected over FireWire 800 and via Thunderbolt with different enclosures.


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