Something new coming to your computer in 2009. This is called USB3 and it will be downward compatable with older usb2. Currently to download 27 gb it takes 14 min, with this you could do it in less than 70 sec. Super Speed is coming soon…. Brought to you by www.asinsights.info

Duration : 0:1:4

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A new version of the ubiquitous Universal Serial Bus (USB) technology will make data rates more than ten times as fast by the addition of fiber optic links alongside the traditional copper wires. The USB 2.0 version that we have now has a maximum data rate of 480 megabits per second so the new USB would be 4.8 gigabits per second. So how would this fast data rate be used and what would be the disadvantages of using fiber optics. One this that is immediately obvious is that USB hard drives would be faster and have greater applications.

But let us check how much easier a USB hard drive would be by checking the calculations. A one Terabyte drive could be copied in almost one and a half seconds. This is assuming that all of the components in your system were fast enough. But this exactly the point. The hard drive is a mechanical device with a spin rate and average seek time and would introduce a data rate reduction from this fact alone.

Also hardware interfaces like a SATA hard drive attached to USB3 port is limited to 150 megabits per second. The value here being the burst speed not a sustained transfer rate. And realistically since most hard drives have only 8 MB of cache or so this would be a short burst of less than a second. Consider on the other hand that Flash memory is slow to write, yet very fast to read. Thats why Windows uses it for ReadyBoost caching. There is extremely low latency but not enough bandwidth to sustain high levels of I/O.

The 4.8 gigabit per second speed of USB3 is the bus speed, that is shared by all devices connected to the same host. So one disk won’t saturate the bus, but if you plug in a bunch of them the bandwidth won’t seem so incredibly massive anymore. There is also bandwidth reserved by isochronous devices. Maybe to utilize the speed with a and external drive, you’d need a RAID external enclosure.
Another thing to consider is the introduction of fiber into the link is how fragile it would make the cable. Would you be able to carry it in your pocket and not fracture? Glass fiber is actually very flexible. You can bend it in any way you want, it won’t break. You can cut it, but that takes considerable force. And if you break the fiber, you’ll break the copper wires as well. The weakest point may just be the connectors. Getting dirt into the connector would probably ruin it.

One problem with the old USB is in the protocol. And, this had to be changed in USB3. USB2 is synchronous that means that data every packet received must be acknowledged in a return packet before the next data packet can be transmitted. This back and forth for each data packet means a lot of wasted time where the channel is essentially idle. Interestingly, sometimes using a shorter cable can make a noticeable improvement.

Firewire for example works well for video streaming from a DV cam because it has very little overhead. Even though USB2 supposedly does 480Mbps, it really can’t do DV because there’s too much overhead. USB3 had to get rid of the CPU dependency and overhead issues. This because Firewire has both synchronous and asynchronous modes. In its async mode, a bunch of packets can be transmitted before any acknowledgment back is required. That’s bad if you have problems with the cables, since it will result in a lot of retransmits, but bad firewire cables are the exception, not the rule. So async is almost always way more efficient than synch.

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There was a recent USB developers conference held at the Doubletree Hotel in San Jose, California on November 17-18, on SuperSpeed USB or USB 3. There was an estimated 1500 attendees: a sign of great amount of interested in the new standard which is not expected to show up for another year. Here is a post summarizing some of what I had been about to gather from various postings on the Web.

The huge feature of USB 3 is of course “SuperSpeed” which is a 5Gb/s transfer mode, “10x” as fast as the current 480Mb/s high speed mode that we have now. But, there is some thought to future expansion. This new protocol allows expansion and the links will negotiate to the highest speed supported. Currently 5Gb/s is the only specified speed.

It looks like the first devices will start to show up in 2010 and they will likely be mass storage. There are no chip sets out yet. There are some vendors with IP (Intellectual Property) to be used in custom designs. The first release of Windows 7 will not have SuperSpeed built in and Microsoft has not set plans to implement it yet. Also Apple is said to be studying the issue. One of the main goals of the standard is to require no host device-driver changes to support SuperSpeed.

How is this greatly enhanced speed accomplished with as much backward compatibility as possible? SuperSpeed traffic can travel in both directions at once (dual simplex). A USB 3 system will basically run a SuperSpeed bus and a USB 2 bus in parallel. The bus has two new shielded twisted pairs to run the SuperSpeed and still has the old unshielded twisted pair USB 2 data pair. Going to these two pairs enables not only simplified bus drivers which don’t have to turn around direction, but also more efficient usage as data can be flowing in both directions at once. You can see that the design of hubs are now twice as complicated as they now have to cope with two parallel, separate busses running through them. Hubs now have extra work to do as SuperSpeed is now really routed through the hubs, not using broadcasts as with USB 2. Of course the USB 2 part of a hub should work as its unchanged from current specs.

Another big thing is better power management. Now high power can use 900 mA and low power, 150 mA. The spec is power management, a lot of effort was put into building power management into all the protocol levels. The main thing here is laptops particularly are able to save power when devices are attached. An attached device doesn’t gain much by power managing, except it is really helping the host. If attached at SuperSpeed a device can now draw 150mA unconfigured and 900mA configured. Quite an amount of current.

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