USB 3.0 SuperSpeed FAQ

What other improvements does USB 3.0 provide?

The enhancements to SuperSpeed USB are not just for higher data rates, but for improving the interaction between device and host computer. While the core architectural elements are inherited from before, several changes were made to support the dual bus arrangement, and several more are notable for how users can experience the improvement that USB 3.0 makes over USB 2.0:

More power when needed

  • 50% more power is provided for unconfigured or suspended devices (150 mA up from 100 mA), and 80% more power is available for configured devices (900 mA up from 500 mA). This means that more power-hungry devices could be bus powered, and battery powered devices that previously charged using bus power could potentially charge more quickly.
  • A new Powered-B receptable is defined with two extra contacts that enable a devices to provide up to 1000 mA to another device, such as a Wireless USB adapter. This eliminates the need for a power supply to accompany the wireless adapter…coming just a bit closer to the ideal system of a wireless link without wires (not even for power). In regular wired USB connections to a host or hub, these 2 extra contacts are not used.

Inno-Logic USB 3.0 SuperSpeed Device controller IP compliant with USB3.0 spec1.0 and AXI interface

Less power when it’s not needed

  • Power efficiency was a key objective in the move to USB 3.0. Some examples of more efficient use of power are:
  • Link level power management, which means either the host computer or the device can initiate a power savings state when idle
  • The ability for links to enter progressively lower power management states when the link partners are idle
  • Continuous device polling is eliminated
  • Broadcast packet transmission through hubs is eliminated
  • Device and individual function level suspend capabilities allow devices to remove power from all, or portions of their circuitry not in use
  • Streaming for bulk transfers is supported for faster performance
  • Isochronous transfers allows devices to enter low power link states between service intervals
  • Devices can communicate new information such as their latency tolerance to the host, which allows better power performance

To paint an accurate picture, not everything in USB 3.0 is a clear improvement. Cable length, for one, is expected to have a significant limitation when used in applications demanding the highest possible throughput. Although maximum cable length is not specified in the USB 3.0 specification, the electrical properties of the cable and signal quality limitations may limit the practical length to around 3 metres when multi-gigabit transfer rates are desired. This length, of course, can be extended through the use of hubs or signal extenders.

Additionally, some SuperSpeed USB hardware, such as hubs, may always be more expensive than their USB 2.0 counterparts. This is because by definition, a SuperSpeed hub contains 2 hubs: one that enumerates as a SuperSpeed hub, and a second one that enumerates as a regular high-speed hub. Until the USB hub silicon becomes an integrated SuperSpeed USB + Hi-Speed USB part, there may always be a significant price difference.

Some unofficial discussion has surfaced on the web with respect to fiber-optic cabling for longer cable length with USB 3.0. The specification makes no mention of optical cabling, so we conclude that this will be defined in a future spec revision, or left to 3rd party companies to implement cable extension solutions for SuperSpeed USB.

Inno-Logic USB 3.0 SuperSpeed Device controller IP compliant with USB3.0 spec1.0 and AXI interface

What new applications does USB 3.0 enable?

In a nutshell, any high-bandwidth device that works with USB 2.0 will become better if updated with USB 3.0 support. At the moment, devices that tax the throughput of USB 2.0 include:

External hard drives – capable of more than twice the throughput available from USB 2.0, not to mention bus-powered portable drives that require non-compliant Y-cables to get the current they require for reliable operation

  • High resolution webcams, video surveillance cameras
  • Video display solutions, such as DisplayLink USB video technology
  • Digital video cameras and digital still cameras with USB interface
  • Multi-channel audio interfaces
  • External media such as Blu-Ray drives

High end flash drives can also push USB 2.0 pretty hard, and oftentimes if multiple devices are connected via hub, throughput will suffer.

USB 3.0 opens up the laneways and provides more headroom for devices to deliver a better overall user experience. Where USB video was barely tolerable previously (both from a maximum resolution, latency, and video compression perspective), it’s easy to imagine that with 5-10 times the bandwidth available, USB video solutions should work that much better. Single-link DVI requires almost 2Gbps throughput. Where 480Mbps was limiting, 5Gbps is more than promising. With its promised 4.8Gbps speed, the standard will find its way into some products that previously weren’t USB territory, like external RAID storage systems.

Inno-Logic USB 3.0 SuperSpeed Device controller IP compliant with USB3.0 spec1.0 and AXI interface

How does USB 3.0 Compare to Competing Interfaces?

Thunderbolt – Developed by Intel, the 10Gb/s bi-directional interface is technically PCI Express on a cable. It was originally designed to use fiber optics, but Intel later went with copper wiring as a mean to reduce cost and to supply power. The expansion bus can support both hubs as well as a daisy chain of up to 7 devices. Thunderbolt, which essentially takes over the Mini DisplayPort, is making its way into all Mac laptops and desktops.

While Thunderbolt is widely reported as USB 3.0 killer, it is not really a competing standard. Rather it is more a niche interface, whereas USB is more of a mainstream port. If you do have multiple RAID arrays and need to push large amount of data to and from it on a daily basis, then yes ThunderBolt is a viable option for you. For everyone else, Thunderbolt may not be cost effective. Just look at all the marketing spin and hype around USB 3.0 being ten times faster and how hard it is actually to get that. Ten times faster is more like 400MB/s as USB 2.0 averages at 40MB/s. To achieve 400MB/s, you need a $500 SSD. Now imagine how much more expensive it will be to get even more speed than what USB 3.0 can deliver and how much additional benefit you’ll get.

Inno-Logic USB 3.0 SuperSpeed Device controller IP compliant with USB3.0 spec1.0 and AXI interface

Firewire – The interface has long been the “forgotten” mass market, high-speed interface standard. Previously available in Firewire 400 or 800 flavors, it has gradually fallen in popularity as USB 2.0 has surged. Apple, the inventor of the original IEEE 1394 “Firewire” standard, has repeatedly sent mixed messages with the ditching of Firewire first from iPods and more recently from the mainstream MacBook laptops (except for the lowest-end MacBook, oddly enough).

In late 2007, the 1394 Trade Association announced Firewire 3200 (S3200) that builds upon the existing Firewire 800 standard that was released in 2002. Utilizing the very same connectors and cabling that is required for Firewire 800, S3200 is basically a drop-in replacement once the internal system components are updated in devices. To date, S3200 has not gained much traction, even in traditional Firewire markets such as digital video.

Firewire’s main claim to fame is that it is a highly efficient peer-to-peer, full-duplex, non-polling data communications protocol with very low overhead. Firewire delivers much higher actual throughput than USB 2.0 and can achieve much closer to its theoretical 800Mbps data rate than USB. Where a Firewire 800 7200-rpm hard drive can deliver sequential transfer rate of around 90MB/s, USB 2.0 hovers more around 40MB/s and USB 3.0 averages at 150MB/s. It remains to be seen what impact S3200 will have on the computing landscape, but with Apple backing Thunderbolt, there’s little hope for Firewire.

Inno-Logic USB 3.0 SuperSpeed Device controller IP compliant with USB3.0 spec1.0 and AXI interface

eSATA, or External SATA – Brought to market in 2004 as a consumer interface targeted directly at the crowded external storage market, eSATA successfully address the issue of the interface bottleneck, and allowed fast hard drives to leverage their performance potential when located external to a server or PC. eSATA supports a data rate of 3.2Gbps, which is more than enough for the fastest hard drives, which can transfer about 120MB/s, easily better than USB 2.0 and significantly better than Firewire 800.

eSATA is not without drawbacks, however. Cable length is limited to a mere 2; it cannot supply power to devices connected on the eSATA bus, and the connectors are neither small nor terribly suitable for consumer devices where aesthetics are important. Over the last several years, eSATA has steadily eroded both USB and Firewire market share in the data storage space, although its applications are limited, and really not well-suited to the portable device market.


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