The third-generation USB interface introduced in 2008. Called "SuperSpeed USB 3.0" (SS USB), it increased the transfer rate from 480 Mbps to 4.8 Gbps and also reduced CPU overhead by no longer continuously polling attached devices. In practice, USB 3.0 devices do not achieve a 1,000% speed increase. For example, a USB 3.0 external hard drive may provide only a 50% improvement over its USB 2.0 counterpart, because the drive's latency and circuitry are limiting factors. Plugs and Sockets Differ Although additional pins were added to 3.0, Type A and Micro USB 2.0 plugs insert into 3.0 sockets for backward compatibility. See USB and USB 3.1.