What You
Need to Know
About USB 3.0
SuperSpeed USB 3.0 Tutorial
USB 3.0 SuperSpeed USB, has some really important advantages for the market: a 10x increase in speed; power management features; and increased bus power for power hungry USB devices. USB 3.0 is new and fast and will be mainstream in the market one day, but it's taking a while to gain significant traction in the market. New xHCI (USB 3.0) Host Controllers are entering the market regularly from companies like NEC, Fresco Logic, and VIA and are already being integrated onto motherboards from ASUS, Gigabyte, and others. The USB-IF Industry group claims that almost 120 USB 3.0 devices are already certified and are shipping in the market, devices such as HD webcams, hard drives, and flash drives. The technology is there, even though one motherboard manufacturer claims to have shipped over 1,000,000 USB 3.0 motherboards, this is still a very small number in comparison to the number of new PC's that ship in the market (Intel claims 1,000,000 a day), let alone the installed base of "legacy" PC's.
USB 3.0 is Relatively Expensive
It will come down in price like everything else to do with technology, but right now it's an expensive feature and not everyone is going to pay for that feature. Increased speed is nice, moving data on and off flash drives and hard drives at 10x the speed is great, but it's generally only the early adopters or power users that are willing to pay for this premium. Cost and Need are intimately linked and when the cost goes down and the premium between USB 2.0 and 3.0 is reduced, we will see more people "needing" USB 3.0's speed.
USB 3.0 and USB 2.0 Cables Are Not the Same
To take advantage of USB 3.0 speeds consumers not only will need a new PC (with USB 3.0 on the motherboard or via add-in card) and a USB 3.0 device (such as a hard drive), but they will also need a new special USB 3.0 cable. USB 2.0 cables have two pairs of wires, one for USB 2.0 data (half duplex) and one for power. USB 3.0 uses an additional two pairs of wires, one for transmitting and one for receiving data (dual simplex), existing USB 2.0 cables don't have these extra wires. One can still use a USB 2.0 cable with a USB 3.0 device, but the system would be limited to USB 2.0 speeds. In fact, if any of the USB host controller, USB connector, USB device, or USB cable are USB 2.0, then the whole system will default to USB 2.0 speeds and functionality, no USB 3.0 features will be realized. USB 3.0 connectors look similar to USB 2.0 connectors but there is a difference if one looks close enough. There were similar "issues" when USB 2.0 came out and many USB 1.1 cables would not work properly with USB 2.0, for more information on the USB 1.1 to 2.0 transition, check out the forums.
USB 3.0 Cable Length Limits are Reduced from 5 meters to 3 meters
USB 3.0 operates at a higher frequency than USB 2.0 and the laws of physics tell us that signals travel shorter distances at higher frequencies. For USB 3.0 the limit is 3 meters (10 feet) as opposed to the 5 meters (16.5 feet) of USB 2.0. This means that standard "passive" USB 3.0 cables will be shorter and certain situations will require a USB 3.0 extender, either an active cable or USB 3.0 extender boxes. USB 2.0 long distance extenders (50 meters and up) are typically found in industrial automation, medical imaging, interactive digital signage, professional Audio/Video, and corporate applications. Shorter distance USB 2.0 extenders, typically repeater cables or hub chains, are found for more consumer applications such as placing a webcam, printer, or SmartPhone sync station in a separate room from the PC. Regardless of the extension application, USB 3.0 extenders will be needed and given the shorter propagation distance of USB 3.0 signals, the volume will likely be much higher than existing USB 2.0 extender products. Certain companies have already announced short distance USB 3.0 active cable extenders. Look for more companies to be delivering new USB 3.0 extension solutions to the market in the future.
USB 3.0 Extenders must have distinct USB 2.0 and USB 3.0 sub-systems
Because USB 3.0 is essentially an "addition" of two extra signal wires on top of the existing USB 2.0 signal wire, USB 2.0 and USB 3.0 are essentially independent systems, they just happen to share the same cable assembly. This means that when one needs connectivity beyond 3 meters, one must extend both USB 2.0 and USB 3.0 as separate systems. This may result in USB 3.0 extenders either neglecting to extend USB 2.0 (careful of compatibility issues!), limiting the extension to 5 meters (the USB 2.0 max distance), or possibly incorporating USB 2.0 extension technology into the USB 3.0 extender to give a proper USB 2.0/3.0 extender. The first two options may be limiting for long distance applications that require full backwards compatibility, while the third may be a more expensive but robust solution. Incidentally USB 2.0 is extended via digital circuitry (such as Icron's ExtremeUSB technology) while USB 3.0 extension utilizes analog high frequency technology such as cable equalization.
USB 2.0 isn't going away
In 2007, USB 1.1 devices were 57% of the total USB shipments in the market with USB 2.0 being 43%. It wasn't until 2008, a full 8 years after USB 2.0's introduction that USB 2.0 shipments overtook USB 1.1 shipments (57% to 43%). Industry analyst firm Instat is predicting USB 3.0 adoption to lag the USB 2.0 adoption rate several years ago. If this proves true, USB 2.0 devices will outship USB 3.0 devices until at least 2018!
Not all devices will transition to USB 3.0. When USB 3.0 is integrated into Intel (and AMD) chips, all PC's in the future will have it, but certain devices such as mice, keyboards, touchscreens, and other devices that don't transfer large amounts of data may opt to go with lower cost USB 1.1 or 2.0 chips inside. Due to the increased number of wires, certain applications where small size is key may also opt to avoid USB 3.0. USB 3.0 offers obvious advantages to hard drives and flash drives and any consumer devices that need to transfer video (e.g. digital cameras), but not all devices will require this and will continue supporting the mature, but inexpensive USB 2.0 protocol.
This article was adapted from material written by Brian Donnelly is the Vice President of Marketing and Business Development for Icron a company focused on USB Extension.
