USB 3.0 vs USB 2.0
Neither Intel nor AMD currently have USB 3.0 support in their chipset. This means a 3rd party chip is needed also for USB 3.0 support on the boards. Most common is the USB 3.0 controller from NEC, which is also included on the Gigabyte P55A-UD6. We got a Buffalo USB 3.0 1TB external drive for testing the USB 3.0 controller. With this drive we did the same tests as for the SATA 6Gbps controller to see how it performs.
But first, we will take a look at the connector for USB 3.0 devices. They differ from USB 2.0 ports, but are fully backwards compatible. USB 3.0 uses a number of extra pins that USB 2.0 ports don't have. Since the extra pins are on the other side of the connector it is still possible to use an USB 2.0 device in a USB 3.0 port and vice versa.
The limit of USB 2.0 was 480Mb/s, or 60MB/s, but due to the way USB 2.0 works it was only possible to reach about half of this speed, around 35MB/s is the limit for the fastest USB 2.0 controllers. USB 3.0 pushes this limit way higher up to 4.8Gbps, a theoretical limit of 600MB/s!
When looking at the performance of USB 2.0 versus USB 3.0 we see that the Buffalo drive connected to the USB 2.0 port the drive gets a maximum speed of about 35MB/s, for read and write, which is about the maximum level of performance we can squeeze out of USB 2.0. With USB 3.0 the drive performs way better, with speeds up to 130MB/s for reading and 105MB/s for writing. It’s also not so far behind SATA 3Gbps, USB 3.0 makes for a worthy replacement of the eSATA interface.
In the Atto benchmark we see about the same performance as in Crystal Diskmark with write speeds over 100MB/s and read speeds that get up to 135MB/s. The internal SATA 3Gbps offers better performance overall, but we can see that USB 3.0 almost three times as fast as USB 2.0!
When connecting the drive to USB 2.0 the graph shows a steady speed at 35MB/s, which means the bottleneck is at the controller and not at the disk. When the same drive uses the USB 3.0 port we see a start at about 120MB/s and the speed stays above 69MB/s, about double the USB 2.0 performance. Average read speed is on par with SATA 3Gbps!
The write performance is the same as the read performance when connecting the drive to USB 2.0, the write performance on USB 3.0 is around 93MB/s, almost 3 times as fast!