All USB hubs support full-bandwidth.Ī high-speed ( USB 2.0) rate of 480 Mbit/s (~57 MB/s) was introduced in 2001. The full-speed rate of 12 Mbit/s (~1.43 MB/s) is the basic USB data rate defined by USB 1.1. It is intended primarily to save cost in low-bandwidth human interface devices (HID) such as keyboards, mice, and joysticks. It is very similar to full-bandwidth operation except each bit takes 8 times as long to transmit. "high-" is alternatively written as "hi-".Ī low-speed rate of 1.5 Mbit/s (~183kB/s) is defined by USB 1.0. USB supports the following signaling rates: The terms speed and bandwidth are used interchangeably. The bus bandwidth therefore only has an effect on the number of channels that can be sent at a time, not the "speed" or latency of the transmission. Overhead is a component of all connectivity standards."įor isochronous devices like audio streams, the bandwidth is constant, and reserved exclusively for a given device. This is 70% of the total bandwidth available.Īccording to a USB-IF chairman, "at least 10 to 15 percent of the stated peak 60 MB/s (480 Mbit/s) of Hi-Speed USB goes to overhead - the communication protocol between the card and the peripheral. Typical hi-speed USB hard drives can be written to at rates around 25–30 MB/s, and read from at rates of 30–42 MB/s, according to routine testing done by CNet.
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