What Is USB 3.0?

A Look At The New SuperSpeed Peripheral Interface

USB 3.0 Standard-B plug
Wikipedia Commons

While the USB 3.0 standard is still the most popular form of external peripheral port, the technology is now being slowly replaced by the latest USB 3.1 standards. It should be important to note that the new technology for the most part is backwards compatible as long as they use the standard Type A and Type B connectors. It will likely face slow implementation just as USB 3.0 did from when it was first introduced.

Universal Serial Bus or USB has been extremely popular for computer peripheral interfaces since it was introduced back in 1996. While the initial release was good for basic devices like keyboards and mice, it lacked speed for higher speed devices such as external storage. The USB 2.0 was generated to improve data rates and this has been the standard for many years now. As data sizes and rates keep increasing, the USB 2.0 specification is now started to feel slow especially for storage compared to the eSATA interface.

It Is All About Speed

The new USB 3.0 SuperSpeed interface is primarily about increasing the overall bandwidth of data that can be transferred between the computer and peripherals. The well entrenched USB 2.0 standard provided theoretical maximum speeds of 480Mbps (or 60MB/s) for devices. In real world usage, it gets maybe one half to two-thirds this amount. That falls well behind the data rates that eSATA can provide external hard drive devices.

USB 3.0 is set to provide 10x the bandwidth of USB 2.0 at 4.8Gbps or 600MB/s. Real world usage will obviously fall below this just like in USB 2.0 but it still provides a major increase that will greatly benefit certain devices.

Another major change that will improve the speed of USB 3.0 is full-duplex communication.

This means that data can be sent to and from the peripheral at the same time. The previous USB 2.0 specification only provided half-duplex, meaning that devices and computers would have to switch off from one another in sending their data.

More And Less Power

One of the big complaints that peripheral manufacturers had with USB 2.0 was the power limitations. Devices were restricted to just 500mA of power from a single powered port. This was not always enough to power some devices requiring that they either piggy off a second USB 2.0 port or have an external power adapter. This is especially true of many larger external storage devices such as DVD burners and desktop sized hard drives. The maximum power for USB 3.0 devices has increased up to 900mA off single bus-powered ports. Additional power is also available for suspended and unconfigured devices.

While the USB 3.0 specifications allow for additional power, they also are looking to reduce the overall power consumption of devices as well. There are a greater number of low powered states available for devices so they when the device or host is idle, less powered is used over the bus to the device. Some signaling changes have also been made so that less broadcast traffic is generated between a host and all the connected devices.

New Cables

In order to achieve these higher data rates, it was necessary to design a new style of USB 3.0 cable. The cable itself will look very similar to the existing USB 2.0 cables. It still uses the same rectangular Type A connector for the vast majority of devices. Rather than just the 4 pin connector of the original USB 2.0 cables, the cable has an additional 4 pins on it in order to support the extra channels for sending data between devices.

Type B cables have also changed in the USB 3.0 specification. Now with Powered-B cables, an additional power (1000mA) can be provided for those devices that require it thus negating the need for external power adapters for more devices.

This will be particularly useful for hubs and external devices such as DVD burners that typically required two USB 2.0 ports to have sufficient power for burning.

Backwards Compatibility

There are a large number of USB 2.0 devices on the market. Because of this, the USB 3.0 specifications were design so that the older devices would properly work with new USB 3.0 controllers and cables. They won't gain any the speed or power benefits of USB 3.0 but they will still function properly. This was critical for USB 3.0 just as USB 2.0 had the requirement for the original USB specifications.


Overall, the USB SuperSpeed of 3.0 specifications are a welcome and needed change for personal computers. With the ever increasing size of data generated, a faster peripheral connector has been needed for some time. The 10x speed boost will greatly improve external storage solution performance placing it nearly at the level of solutions such as eSATA but with a wider range of peripheral options. The new power profiles will also greatly help reduce the need for peripherals that require external power adapters or using multiple ports.