masrevistas.com

USB 3.0 (following Wireless USB) is the next major revision of the ubiquitous Universal Serial Bus, created in 1996 by a consortium of companies led by Intel to dramatically simplify the connection between host computer and peripheral devices. Fast forwarding to 2009, USB 2.0 has been firmly entrenched as the de-facto interface standard in the PC world for years (with about 6 billion devices sold), and yet still the need for more speed by ever faster computing hardware and ever greater bandwidth demands again drive us to where a couple of hundred megabits per second is just not fast enough.

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.
• 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.

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.