supports the following signaling rates:
The terms speed and bandwidth are used
interchangeably. "high-" is
alternatively written as "hi-".
original USB 1.0 specification, which
was introduced in January 1996, defined
data transfer rates of 1.5 Mbit/s "Low
Speed" and 12 Mbit/s "Full Speed".
The first widely used version of USB was
1.1, which was released in September 1998.
The 12 Mbit/s data rate was intended for
higher-speed devices such as disk drives,
and the lower 1.5 Mbit/s rate for low
data rate devices such as joysticks. A
low-speed rate of 1.5 Mbit/s (~183 kB/s)
is defined by USB 1.0. It is very similar
to full-bandwidth operation except each
bit takes 8 times as long to transmit.
It is intended primarily to save cost
in low-bandwidth human interface devices
(HID) such as keyboards, mice, and joysticks.
The full-speed rate of 12 Mbit/s (~1.43
MB/s) is the basic USB data rate defined
by USB 1.1. All USB hubs support full-bandwidth.
USB 2.0 specification was released in
April 2000 and was standardized by the
USB Implementers Forum (USB-IF) at the
end of 2001. Hewlett-Packard, Intel, Lucent
Technologies (now Alcatel-Lucent), NEC
and Philips jointly led the initiative
to develop a higher data transfer rate,
with the resulting specification achieving
480 Mbit/s, a fortyfold increase over
the original USB 1.1 specification. A
high-speed (USB 2.0) rate of 480 Mbit/s
(~57 MB/s) was introduced in 2001. All
hi-speed devices are capable of falling
back to full-bandwidth operation if necessary;
i.e. they are backward compatible with
USB 1.1. Connectors are identical for
USB 2.0 and USB 1.x.The theoretical maximum
data rate in USB 2.0 is 480 Mbit/s (60
MB/s) per controller and is shared amongst
all attached devices. Some chipset manufacturers
overcome this bottleneck by providing
multiple USB 2.0 controllers
USB 3.0 specification was published on
12 November 2008. Its main goals were
to increase the data transfer rate (up
to 5Gbps), to decrease power consumption,
to increase power output, and to be backwards-compatible
with USB 2.0. USB 3.0 includes a new,
higher speed bus called SuperSpeed in
parallel with the USB 2.0 bus. For
this reason, the new version is also called
SuperSpeed. The first USB 3.0 equipped
devices were presented in January 2010.
A SuperSpeed (USB 3.0) rate of 4800 Mbit/s
(~572 MB/s). The written USB 3.0 specification
was released by Intel and partners in
August 2008. The first USB 3 controller
chips were sampled by NEC May 2009
and products using the 3.0 specification
arrived beginning in January 2010.
USB 3.0 connectors are generally backwards
compatible, but include new wiring and
full duplex operation.
name ('A' connector
name ('B' connector)