USB 3: The future arrives

USB 3: The future arrives

It’s always the same: you wait ages for a bus, then two come along at once. This month, both USB 3 and SATA/600 arrived in the form of the Asus U3S6 PCI Express x4 combined controller card.

Introducing SuperSpeed USB

USB 2 has served us well, but high-bandwidth devices – most notably external hard disks – can be held back by its maximum transfer rate of 480Mbits/sec. Enter USB 3, and a new operational mode dubbed SuperSpeed that boosts transfer rates by a factor of ten.

That’s enough bandwidth to allow even the fastest hard drive to achieve full potential, and opens up possibilities for high-resolution USB display devices, too.

We installed the U3S6 card in a Core i7-920 system and timed how long it took to copy files between a RAM disk and a pre-production external USB 3 hard disk.

The test was run with a folder of 3,000 files totalling 300MB, and then with one 650MB file. We repeated the test with the drive connected to a USB 2 port.

As our graph opposite shows, with the USB 3 connection enabled the drive’s performance was more than twice that of USB 2 in our multifile test. With a single 650MB file the performance improvement was almost four-fold.

We also compared eSATA performance, using the A-Listed Iomega Professional External Hard Drive. The results were mixed, but the SuperSpeed did close the performance gap. We expect eSATA may well fall into disuse as USB 3 gains currency.

Compatibility and connectors

USB 3 connectors look familiar, but peer inside the plug and you’ll see five new pins alongside the traditional four.

These extra data lanes make SuperSpeed possible, so top performance requires a USB 3-compatible cable. The sockets work with older cables and devices, so you can mix old and new hardware.

The only sticking point is that a USB 3 cable won’t fit into a USB 2 device. But that has a benefit, too, as the larger plug lets you identify a USB 3 cable at a glance. Manufacturers have made it easy to recognise USB 3 ports by colour-coding them with blue plastic.

USB 3 is a great upgrade, but it may take a while to become mainstream. Intel and AMD have yet to integrate a controller into a chipset, so for the time being we expect that only premium motherboards will support it. Still, the U3S6 controller card is tempting, selling for around $45.

click to view full size image
File transfer speeds of USB 2, USB 3 and eSATA compared


Internal drives also get a boost this month, courtesy of SATA/600. The new standard maintains compatibility with SATA/300, but doubles its bandwidth to 6Gbits/sec — yielding a usable transfer rate of 600MB/sec once you factor in SATA’s 10-bit encoding overhead.

It’s a timely upgrade, as solid-state drives are on the verge of outpacing the old SATA interface. Last year in the PC Authority Labs we saw the Intel X25-M SSD achieve 75% saturation of a SATA/300 link.

Mechanical drives can benefit, too. Not for big data transfers – spinning platters typically max out at 110MB/sec – but the RAM buffers in modern drives can send small chunks of data back and forth at much higher speeds.

To test the benefit, we used Seagate’s new Barracuda XT – the first SATA/600 drive we’ve seen, with a capacity of 2TB and a 64MB RAM buffer. We installed it as the system disk in our Core i7-920 test rig and ran the PC Authority benchmarks twice, first using SATA/300 and then SATA/600.

As our graph shows, switching to SATA/600 raised the system’s overall benchmark score from 1.78 to 1.84 – a leap equivalent to a minor CPU upgrade.

The benefit was concentrated in certain tasks, particularly our 2D graphics tests, which work intensively with a relatively small set of large files.

And that limited boost comes at a price. Although the controller card is cheap, the Barracuda XT itself retails at $430. Shop around and you’ll find standard 2TB drives for $200 less.

For now, we’d hold off investing in SATA/600, except for fast SSDs or striped arrays that will derive a real benefit.

All the same, prices will surely fall as we move through 2010, until SATA/600 replaces SATA/300 as a matter of course, and brings a welcome performance boost for all.
This reviewgroup appeared in the March, 2010 issue of PC & Tech Authority Magazine

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