Feeds

Inside USB 3.0

What makes SuperSpeed tick

Build a business case: developing custom apps

Since USB 3.0 incorporates USB 2.0, plugging a USB 3.0 printer into a USB 2.0 port on your PC will still work, but without the benefits of the faster bus. The USB 2.0 add-on doesn't even need to know the computer it's connected is a SuperSpeed device, it'll just work as if the PC has USB 2.0. Existing drivers will continue to work.

Bus Architecture

USB 3.0's dual-bus architecture

SuperSpeed USB has a dual-bus architecture to allow hosts to run USB 3.0 right alongside USB 2.0 - hence that USB 2.0 cable tucked inside the USB 3.0 cord. But while hosts and hubs will be able to operate USB 2.0 and USB 3.0 buses simultaneously, plug-in peripherals will not.

So there'll be no combining both buses to get an aggregate bandwidth of 5.4Gb/s.

However, it does mean that a brand spanking new netbook with USB 3.0 ports but running Windows XP as its OS won't lose USB functionality, only the SuperSpeed operation.

Running the USB 3.0 part independently of the USB 2.0 bus is necessary because the new bus uses different protocols, though it retains USB 2.0's data transfer types and pipe model to make it easier for driver writers to make use of existing code. SuperSpeed transmits data in packets, as USB 2.0 does, but this time devices explicitly route packets from the source to the target. Compare that to USB 2.0, which simply broadcasts all packets to all connected devices whatever they may be and whether they're the intended recipient or not.

The new approach has a couple of key advantages. First, it means you'll be able to connect many more devices: up to 127 of them chained in up to five tiers of hubs, each of which can drive up to 15 ports. Secondly, it makes for a far more power-efficient bus.

Packets are sent asynchronously and assembled into files at the end of their journey. Links in the route-chain are used only when they're needed. There's no need for devices to continually poll the link for incoming data.

Send a file to a USB Flash drive, and the packets will move from device to device down the chain according to a direct route encoded into the packets' headers. Each step of the journey is initiated at a signal from the host, which knows where each packet is coming from and where it's going.

USB 3.0 SuperSpeed

Hubs are more like routers in USB 3.0

The host is always part of the chain, so a packet sent from a connected camera to a Flash drive is routed first to the host and then out to the storage gadget.

The essential guide to IT transformation

More from The Register

next story
So, Apple won't sell cheap kit? Prepare the iOS garden wall WRECKING BALL
It can throw the low cost race if it looks to the cloud
End of buttons? Apple looks to patent animating iPhone sidewalls
Filing suggests handset with display strips
One step closer to ROBOT BUTLERS: Dyson flashes vid of VACUUM SUCKER bot
Latest cleaner available for world+dog in September
Samsung Gear S: Quick, LAUNCH IT – before Apple straps on iWatch
Full specs for wrist-mounted device here ... but who'll buy it?
Apple promises to lift Curse of the Drained iPhone 5 Battery
Have you tried turning it off and...? Never mind, here's a replacement
Now that's FIRE WIRE: HP recalls 6 MILLION burn-risk laptop cables
Right in the middle of Burning Mains Man week
Apple's iWatch? They cannae do it ... they don't have the POWER
Analyst predicts fanbois will have to wait until next year
Reg man looks through a Glass, darkly: Google's toy ploy or killer tech specs?
Tip: Put the shades on and you'll look less of a spanner
HUGE iPAD? Maybe. HUGE ADVERTS? That's for SURE
Noo! Hand not big enough! Don't look at meee!
prev story

Whitepapers

Top 10 endpoint backup mistakes
Avoid the ten endpoint backup mistakes to ensure that your critical corporate data is protected and end user productivity is improved.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Backing up distributed data
Eliminating the redundant use of bandwidth and storage capacity and application consolidation in the modern data center.
The essential guide to IT transformation
ServiceNow discusses three IT transformations that can help CIOs automate IT services to transform IT and the enterprise
Next gen security for virtualised datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.