USB 3.0 provides faster speed and more efficient power management than USB 2.0. Externally, the inside of USB 2.0 connector is white or black, while the inside of USB 3.0 is blue, which is easy to distinguish. In addition, USB 2.0 has 4 connector wires, and as for USB 3.0, it has 9 connector wires.

Highlights of USB 3.0 and its advantages over USB 2.0

Transmission rate: USB 2.0 provides a transmission rate of 480 Mbps, and USB 3.0 provides a transmission rate of 4.8 Gbps, which is 10 times faster than that.

Add another physical bus: the number of wires has doubled, from 4 to 9. Because extra wires need more cable and connector space, a new connector is designed.

Power consumption: the power consumption of USB 2.0 is 500 mA, while that of USB 3.0 is as high as 900 mA. USB 3 devices provide more power when needed, but save power when idle.

More bandwidth: USB 3.0 is not a one-way communication, but uses two one-way data paths, one for receiving data and the other for transmitting, while USB 2.0 can only handle data in one direction at any time.

Improve bus utilization:

 A new function (using data packets NRDY and ERDY) has been added, which allows the device to asynchronously notify the host that it is ready.

When data is transmitted through USB 3.0 devices, cables and connectors, a transaction is initiated by the host, and then the device responds. The device either accepts the request or rejects it. If accepted, the device sends data or accepts data from the host. If the buffer space or data is insufficient, it will respond with a NRDY signal, telling the host that it cannot process the request. When the device is ready, it will send an Endpoint Ready (ERDY) to the host, and then the host will reschedule the transaction.

Physical differences

USB 3.0 connector is different from USB 2.0 connector. 3.0 connector is usually painted blue inside, so it can be easily distinguished from the outside.

downward compatibility

USB 3.0 is compatible with USB 2.0. However, if you use USB 2.0, the performance of 3.0 devices will not be reflected, and the speed and power advantages will not be fully realized.

If USB 3.0 sockets are physically matched, they are electrically compatible with USB standard 2.0 device plugs. USB 3.0 type-A plug and socket are fully backward compatible, and USB 3.0 type-B socket will accept USB 2.0 and earlier plugs. However, USB 3.0 B plug is not suitable for USB 2.0 and earlier sockets. Of course, a usb converter can also be used.