What is the difference between USB 2.0 and USB 3.0?

 

What is the difference between USB 2.0 and USB 3.0?

When comparing 2.0 and 3.0 there are a few major differences. First the transfer rates: USB 2.0 offers transfer rates of 480 Mbps and USB 3.0 offers transfer rates of 4.8 Gbps - that's 10 times faster. Note that the transfer speeds also depend on the device in use in addition to the bus type and USB ports and cables.

Bus Type Max Transfer Rate USB 3.0 Transfer Speed USB 2.0 Transfer Speed
PCIe 1.0a 2.5 Gbps 2.5 Gbps 480 Mbps
PCIe 2.0/2.1 5 Gbps 4.8 Gbps 480 Mbps
PCIe 3.0 8 Gbps 4.8 Gbps 480 Mbps
ExpressCard 1.0 2.5 Gbps 2.5 Gbps 480 Mbps
ExpressCard 2.0 5 Gbps 4.8 Gbps 480 Mbps


The second main difference is the addition of another phsyical bus - doubling the amount of wires, from 4 to 8. Additional wires require more space in both the cables and connectors, so there are new types of connectors for the B Male and Micro B Male. These connector types are larger than the 2.0 equivalents to accomodate the additional wires and cannot be used with 2.0 ports (see diagram below).

USB-connectors-edu.png

Finally the last main difference is the available power and power management of the 3.0 products. USB 2.0 provided up to 500 mA whereas USB 3.0 provides up to 900 mA, allowing power hungry devices to now be bus powered. In addition the 3.0 technology allows better power efficiency with less power for idle states or to remove power completely when not in use