SuperSpeed USB 3.0 FAQ

18 January 2013, Comments: 29

Dubbed SuperSpeed USB, USB 3.0 promises a major leap forward in transfer speeds and capability, while maintaining backwards compatibility with USB 2.0 devices. It may sound straightforward, but a lot has had to change; in this FAQ we will address the most common questions about USB 3.0 and explain in plain English what it all means.

What is USB 3.0?

USB 3.0 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 PC and peripherals. It is in fact the first major revamp (following Wireless USB and USB On-the-Go) to stay current with modern demands for connectivity bandwidth.

Fast forwarding to 2012, USB 2.0 has been firmly entrenched as the de-facto interface standard in the PC world for a decade. Yet there’s still the need for more speed by ever greater bandwidth demand from devices, such as a SandForce flash drive, 7200-rpm hard drive or dual-head HD video adapter, again drive us to where a couple of hundred megabits per second is just not fast enough.

In 2007, Intel demonstrated SuperSpeed USB at the Intel Developer Forum. Version 1.0 of the USB 3.0 (confusing, isn’t it?) specification was completed on November 17, 2008. As such, the USB Implementers Forum has taken over managing the specifications and publishes the relevant technical documents necessary to allow developers and hardware manufacturers to begin to develop products around the USB 3.0 protocol.

What are the major USB 3.0 improvements?

In a nutshell, USB 3.0 promises the following:

  • Higher transfer rates (up to 4.8Gbps)
  • Increased maximum bus power
  • New power management features
  • Full-duplex data transfers
  • Support for new transfer types
  • Backward USB 2.0 compatibility
  • New connectors and cables

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, such as a 22″ monitor or speedy portable drive, 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
What improvements are made to USB 3.0 cables & hubs?
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 USB 3.0 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 plus 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, video capture, webcams, video adapters, multi-channel audio interface and last but not least, Blu-ray burners. 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 to 10 times the bandwidth available, USB video solutions should work that much better. Single-link DVI requires almost 2Gbps throughput. Where 480Mbps was limiting, 4.8Gbps is more than promising. At such speed, the standard will find its way into some products that previously weren’t USB territory, like external RAID storage systems.
Is faster USB 3.0 already planned?
A rather surprising announcement was made during CES 2013 that the official USB promoter group has a grand plan to double speed of USB 3.0 to 10Gbps from current 4.8Gbps. This is a clear response to the threat of Thunderbolt which is still slow at gaining traction. Though details regarding so-called USB 3.1 are still sketchy on the technical aspects as of this writing.Existing connectors would still work, yet new cables may not be needed if they are tested capable of operating at 10Gbps. There will even be improved data-encoding efficiency for applications like video and audio. Software stacks and class protocols will also work seamlessly with the amended version of USB 3.0.

What’s certain is that the new specs won’t be completed until later half of 2013. First wave of “double-speed” USB 3.0 products likely won’t hit stores until 2015. Frankly speaking, there’s a 8 year gap between USB 3.0 and 2.0; few really expected a revision just 5 years after the formal introduction of the current standard in 2008.

How does USB 3.0 achieve the extra performance?
USB 3.0 achieves the much higher performance by way of a number of technical changes. Perhaps the most obvious change is an additional physical bus that is added in parallel with the existing USB 2.0 bus.This means that where USB 2.0 previously had 4 wires (power, ground, and a pair for differential data), USB 3.0 adds 4 more for two pairs of differential signals (receive and transmit) for a combined total of 8 connections in the connectors and cabling. These extra two pairs were necessary to support the SuperSpeed USB target bandwidth requirements, because the two wire differential signals of USB 2.0 were not enough.

Furthermore, the signaling method, while still host-directed, is now asynchronous instead of polling. USB 3.0 utilizes a bi-directional data interface rather than USB 2.0′s half-duplex arrangement, where data can only flow in one direction at a time. Without getting into any more technical mumbo jumbo, this all combines to give a ten-fold increase in theoretical bandwidth, and a welcome improvement noticeable by anyone when SuperSpeed USB products hit the market.

Isn’t USB 2.0 fast enough?
Well, yes and no. USB 2.0 for many applications provides sufficient bandwidth for a variety of devices and hubs to be connected to one host computer. However, with today’s ever increasing demands placed on data transfers with high-definition video content, terrabyte storage devices, high megapixel count digital cameras, and HD video capture and portable media players, 480Mbps is not really fast anymore.Furthermore, no USB 2.0 connection could ever come close to the 480Mbps theoretical maximum throughput, making data transfer at around 320Mbps (40MB/s) – the actual real-world maximum. Similarly, USB 3.0 connections will never achieve 4.8Gbps. We will likely see a real-world maximum rate of 400MB/s with overheads. At this speed, USB 3.0 is a 10x improvement over USB 2.0.
What operating systems support USB 3.0?
Apple Mountain Lion (10.8) and Microsoft Windows 8 – both shipping in 2012 – came with native USB 3.0 support whereas third party drivers for Windows 7, Vista and XP have been availablesince 2008.Mountain Lion
Apple has remained silent on the issue of USB 3.0 support in Mac OS X even when the public knows well that Macs will eventually get Ivy Bridge (Intel third-gen Core i CPUs) whose Panther Point platform comes with USB 3.0, for free. For a while, there was an ongoing debate over whether or not Apple will adopt USB 3.0 given its enthusiasm for Thunderbolt. But in mid-June 2012 at WWDC, Apple finally introduced USB 3.0 to its entire line of MacBook Air and MacBook Pro as part of Ivy Bridge processor refresh and at the same time, OS X Mountain Lion (10.8) was announced to ship in the following month. So, USB 3.0 support on Macs officially begins with Mountain Lion.

LaCie and HighPoint have developed their own USB 3.0 driver for Mac to work with Mac OS X from Leopard (10.5). LaCie solution however only works with its own drives, including FastKey SSD, 2big RAID, Rikiki portable drive.

Windows 8
In October 2012, Microsoft started shipping Windows 8 with built-in USB 3.0 support. The Windows team said it has written completely new software stack for USB 3.0 rather than adding support on top of the current USB 1.1/2.0 drivers. To save time, work on USB 3.0 software stack actually began way before there were any peripherals so the engineers had to come up with something called virtual USB 3.0 devices for simulations. In retrospect, the team probably has plenty of time since USB 3.0 wasn’t an instant hit and was slow to take off.

Built-in support for USB Attached SCSI Protocol (UASP) will come as well. This will supplement Bulk-Only Transport (BOT) which has its roots in USB 1.1. USAP class driver, which benefits mass storage applications, adds command queuing to deal with multiple concurrent requests and offers lower overheads than BOT protocol. In other words, you will see even faster transfer rate and lower CPU usage. Only a handful of USB 3.0 drives support USAP as of this writing but on Windows 8, USAP mode will only kick in when the drive interfaces with a USB 3.0 host controller that conforms to xHCI 1.0 specification.

Windows 7, Vista & XP
Intel, Renesas and other fabs have been updating their own stable USB 3.0 software stacks for Windows 7, Vista and XP in the last several years. So there’s no reason for us to believe Redmond is in any hurry to bring USB 3.0 support via service packs to the aforementioned Windows platforms.

Will my existing peripherals still work? How will they co-exist?
The good news is that USB 3.0 has been carefully planned from the start to peacefully co-exist with USB 2.0. First of all, while USB 3.0 specifies new physical connections and thus new cables to take advantage of the higher speed capability of the new protocol, the connector itself remains the same rectangular shape with the four USB 2.0 contacts in the exact same location as before. Five new connections to carry receive and transitted data independently are present on USB 3.0 cables and only come into contact when mated with a proper SuperSpeed USB connection.
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  • http://pulse.yahoo.com/_JLE6OHMERVRVN23TAUGLEQPBLQ Stan

    I know I am a redneck from simple ole Alabama and we ain’t up tuh date wit all yur fancy jabber jawin. Maybe we might be taken more seriously if it were known more universally at least where a lot of us live is near nuclear plants, rocket plants, and NASA (aka:Rocket City, Huntsville, AL). Just answer the question instead of giving a history lesson on USB’s origin and development. I started out just wondering if I was going to have to ditch everything with a USB2 connection to find out about compatibility of any new peripheral device I may add and wind up at the end of Mr. I,like to read my own article. In fact that is where I will begin looking for answers from now on at the end of the search.

    • stanley alvarez

      amazes me how people do something for free, take the time to try to put
      something out there useful for the public at no cost to them and then
      they have the audacity to complain.  as for information provided here it
      is quite thorough and appreciated.  fyi for anyone looking for a more
      basic explanation, fine tune your search criteria and if you don’t like
      what you see at first try another selection.  my thanks to the author
      for providing us a service/information free of charge. honest to
      goodness southern hospitality still exist out there though, our family
      for one has not forgotten that part of our heritage. fyi, my mother’s family settled tennessee back when it was carolina long before trailer parks “rednecks.” trolls
      unfortunately know and care little about common courtesy and know no
      boundaries, on so many levels.  back on topic, looks like i will be
      needing to get some new cables to hook the external drives.

  • jeff005ab

    There is a really good update to the USB 3.0 faq here. 
    http://www.ptgrey.com/news/usb3.asp#FAQ
    Its geared towards using USB 3.0 as a camera streaming interface but it has some good info on real life throughput (280 MByte/s)

  • http://laussieswritingblog.blogspot.com/ Denise Covey

    yeh USB 3 seems ta do it all!!

  • Sid Farkus

    I do live broadcasts on USTREAM.TV using USB 2.0 cams and cables.Bandwidth  is an issue when using two or more cams. If I add USB 3.0 connectors will I see any increase of ava. bandwidth?

  • Sid Farkus

    So adding USB 3.0 to a PC with USB 2 web cams and cables will not increase the ava bandwith, correct?

  • gadgetronica

    With this sort of advancement in technology are we still going to be tethered to 16 feet (maximum) cables with active repeaters for extended lengths? Yes, we probably will still be limited to the 16 foot barrier without the repeaters. So far, USB 3.0 still runs on copper cabling with most likely the same inherent limitations.Source: http://gadgetronica.com/technopedia/USB-3.0-Data-Transfer-Redefined.html

  • Tom Post

    Sadly, I am using Linux Kernel 2.6.35 (Ubuntu 10.10) and USB 3.0 does not work reliably.  Sometimes it is recognized and sometimes it is not (a USB 3.0 pci-express card with 2 ports).  And I never got a USB 3.0 hub with 4 ports to work.  I am not alone.  A Google search shows a lot of frustration trying to get USB 3.0 to work on all flavors of Linux and even newer versions.

  • http://www.facebook.com/dont.followshaik Shaik Saif

    wowowo what an improvement in serial buses 

  • Steffan Koch

    Do you have to have 3.0 connections on your computer to have the full advantage of the speed it offers??

    • aghast1000

       Of course. Otherwise you’ ll just get USB 2.0 speeds.

  • http://twitter.com/CompRep4U Computer Repair 4U

    Just bought a new motherboard with USB 3.0 and I am very impressed with the speed when hooking up my external drive.

  • Saurabh Joshi

    USB 3.0 = Awesomeness

  • PavolN

    Please can you send me website with latest usb 3.0 drivers. Site http://www.usb3-drivers.com dont includes latest Fresco drivers :-(

  • http://profile.yahoo.com/EMU2FV332QGA2KHINZ3PFUJOMA Ken

    Too bad every single system I’ve seen using USB 3.0 freezes.

    • EdTwidley

      Too bad every single system I’ve seen using USB 2.0 freezes… and same for USB 1… hmm… and Firewire… and old school parallel ports.

      I’m working on a laptop this very moment that uses USB3 and doesn’t have a problem with it.

  • http://twitter.com/mickbanks Mike

    I wonder why we never saw USB3 on the iPad3… or Apple’s ThunderBolt for that matter 

    • nztdm

      no tablet has >40MB/s flash memory yet. and it’s Intel Thunderbolt, not Apple. It was actually a Sony laptop that came with a thunderbolt port first.

      • drx1

        oye – AFAIK – Apple and Intel developed Thunderbolt (also called LightPeak – iirc). Apple is not often first, yet they frequently build a better implementation. They ran TB on some early computers and the nice thing is – you could easily have a TB to USB 3 adaptor – TB certainly has the bandwidth for this.

        And now TB2 has been out for some time … 20Gbps full duplex is not all that bad.

        I do think TB and USB 3 need some driver work, however … but they are both new.

  • Dave Brown

    If I have a USB 3.0 host controller, a USB 3.0 4-port hub, and  4 USB 2.0 devices.  Will each of the USB 2.0 devices operate at full 2.0 speed (480Mbps)?
    Does using a USB 3.0 controller & hub make the bandwidth of 3.0 available to share across 2.0 devices, or will the whole arrangement default back to USB 2.0, 480Mbps total bandwidth?

    • the voluntary hostage

      I think it depends on the hub. More than likely, it should use the USB 3.0 speed to support more than one USB 2.0 device due to the idea you might hook up say a mouse and keyboard alongside a USB hard drive. While the drive would be USB 3.0, I do not see any mice and keyboards being USB 3.0 anytime soon since they have been very happy at 100mA give or take. I have yet to see anything higher then 150mA on mice yet except a wireless mouse that had a battery charger built into the receiver.

      Certain devices will likely never use USB 3.0 so a mixed config must be acceptable, maybe giving certain USB devices a higher priority like the mouse and keyboard as well as webcams. However, I would rather have my file transfer take a minute longer than to have my mouse and keyboard lock up on me or my webcam go choppy.

      So by default of what the real world requirements are for such a device as a USB hub, I would expect that you could use multiple USB 2.0 devices at full speed from a USB 3.0 hub if you are working from a USB 3.0 port to start with. If plugging in a USB 2.0 or legacy device would disable all USB 3.0 support, that would be self defeating.

  • http://profile.yahoo.com/N7NDYR7U7VMB5HS6JMEH3WORQY PaigeMHughes

     So, if my laptop has USB 2.0 ports, would it make any difference in transfer speeds to buy a USB 3.0 external hard drive instead of a 2.0… I’m thinking that my transfer speeds are going to max out at the 2.0 capabilities, but I don’t know enough to be certain.

    • drx1

      The internal HDD in the USB device is mostly likely faster (but not necessarily) than a USB 2.0 HDD. That said, the USB 3 device would be limited by the USB 2 specification/drivers/etc…

      The good news would be once you upgraded or purchased a new system that includes USB 3, you would get the full benefit.

  • Megha

    Do any of the USB3.0 mass storage devices listed above support the UAS protocol?I want to do some throughput measurements ,but can’t figure out if the USB3.0 listed actually support the UAS protocol!

  • drx1

    USB 3.0 – part deux? So where is the ‘double speed USB 3.0′? I don’t often pay full attention to CES. CES 2014 just finished … I don’t know anyone talking about USB 3.0 or otherwise…

    TB is more prosumer/professional connection. TB2 (20Gbps/ full duplex) is already out – damn fast – yet not cheap. USB 3 still seems like it is half supported:
    1) most USB 3 PCIe cards are only PCIe 1x – yet if you are PCIe v1, 2 or possibly 3 – there won’t be much bandwidth for the card – they should be 4x to 8x.
    2) most USB 3 PCIe cards have only two USB 3 ports. They should have at least 4 ports – maybe more … and of course be use 4 to 8 (maybe even 16) lanes for better bandwidth.
    3) USB hubs seems fairly rare … and pricey. It is 2014, I would have thought things would farther along – maybe i missed something? USB 3 hubs would be important – see point # 2.
    — awaking an old thread (hopefully)!

  • Robert Mason

    need an answer.. have a usb3 external hard drive with its own wall wart for power.Thw drive uses a standard usb3 cord which came with the unit. IT appears that the internal power is not isolated from the usb3 connector so power is actuallgoing out of the device and into the computer.This seem wrong to me but no one so far seem to have an answer for me. I would think isolation would be mandatory??

    • the voluntary hostage

      It’s likely isolated in some way likely done with a scotchy diode. I will not get into what that is but it would provide 2 way isolation from both power sources while allowing them to both to power the load.

      Smart engineering would only have one power source per voltage. Hard drives need 5 volts while other need 12 volts. USB will provide some 5 volt power enough for most hard drives, but 12 volt would have to be external. It would not shock me to see an external 5 volt source and you have 2 parts that would need 5 volt for the controller and the drive itself. I suspect the 5 volt even on USB 3.0 is cutting it a bit close to run both I used to work for a TV repair tech.

      The tech reason you would not want to use 2 power sources. Well isolating them with diodes would create a voltage drop of .7 volts so your 5 volts would become 4.3. If the diode was very over rated amp wise, you might get the drop down to .6 still not good.

      The second issue is the 2 power sources would be affected by load differently and cause strange and sudden changes in voltage. When the amperage changed, this becomes less of an issue if the 2 sources were powering different loads such as the USB to power the drive controller and the AC adapter to power the had drive.

      Now without any way to provide isolation on the USB end, you would likely have a 10k ohm leak from the AC adapter at 5 volts. So, if you got a power surge, it could fry the data transfer hardware of the USB 3.0 and not really affect the 5 volt power all that much. So, this really comes down to how much surge protection is in the wall wart if the AC is big heavy and I suspect it is.

      If I was the engineer, it would contain an iron core transformer and large low voltage capacitor before and after a voltage regulator. I cannot say what they did or did not do in making of this hard drive. If the external wall wort is big and heavy weighing close to a pound or more and bigger than 1.5 times the size of your fist, you’re likely fine or just get a high end surge suppressor that will provide some protection.

      • Robert Mason

        Thank you voluntary hostage. Your explanation answers my question. This unit has only a small light wall wart .Doubtful it offers any protection. I have found other digital devices in my search that have a switch built into the power input on the device to disconnect the incoming USB3 power lines from the device so there would be no crossover or two feed of power. I am still wondering how to find a safe properly built external drive/case without testing each one. The vendors seem to be clueless about this problem.

  • Gilad

    USB3 offer a much faster bandwidth than USB2 but, technically, in the price of more wires that resolves in a thicker cable.

    USB3 is build with 9 wires, 4 are standard USB2 and 5 are the USB3 serial (2 differential transmit, 2 differential receive and one GND)

    In an effort to make a thin & flexible cable, would it be possible to make a 5 wire cable, just with the USB3 wires? Assuming that both sides of the cable are USB3? Nothing on this in the standard…

    Before I order connectors and try this myself…

    Thanks