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USB 2.0 has
been the ubiquitous external data connection standard for all types of
computers since its release in 2000. However with the phenomenal
increase in casual users storing large files such as video, audio, and
programs, demand for larger capacity hard drives has also increased
drastically. The limited maximum transfer rate of USB 2.0 at about
30MB/s (megabytes per second) has become inadequate for the general
user. Many computer users are now relying on other types of data
interfaces, such as Firewire 800, eSATA / SATA, or Gigabit networks, to
transfer large amounts of data between their mass storage devices.
USB 3.0, also
known as the SuperSpeed bus, was designed to address the limitation of
slow transfer rate. USB 3.0 introduces a fourth transfer mode of 5Gbps
(gigabits per second). This new transfer mode upgrades the USB
technology to support a maximum throughput of about 600MB/s while still
maintaining backwards compatibility with the older signaling rates.
|
USB Signaling Rate Chart |
|
Low Speed |
USB 1.0 |
1.5 Mbps |
|
Full Speed |
USB 1.1 |
12 Mbps |
|
Hi-Speed |
USB 2.0 |
480 Mbps |
|
SuperSpeed |
USB 3.0 |
5 Gbps |
|
This allows a
USB 3.0 mass storage device to be connected onto a legacy USB 2.0/1.1
port, and likewise. It is important to note that there are now two types
of connector and plug combinations in USB 3.0 specification, SuperSpeed
standard A and SuperSpeed standard B. SuperSpeed standard A plugs will
fit legacy A receptacles but SuperSpeed standard B plugs will not fit
into legacy standard B receptacles. Below are charts comparing the
pinouts of the SuperSpeed standard A plug and the SuperSpeed standard B
plug.
| High-Speed USB
2.0 A plug pinout |
SuperSpeed
standard A plug pinout |
SuperSpeed
standard B plug pinout |
 |
 |
 |
|
1 |
VBUS |
Red |
|
2 |
D- |
White |
|
3 |
D+ |
Green |
|
4 |
GND |
Black |
|
Shell |
Shield |
Connector
Shell |
|
|
|
1 |
VBUS |
Red |
|
2 |
D- |
White |
|
3 |
D+ |
Green |
|
4 |
GND |
Black |
|
5 |
StdA_SSRX- |
Blue |
|
6 |
StdA_SSRX+ |
Yellow |
|
7 |
GND_DRAIN |
GROUND |
|
8 |
StdA_SSTX- |
Purple |
|
9 |
StdA_SSTX+ |
Orange |
|
Shell |
Shield |
Connector
Shell |
|
|
|
1 |
VBUS |
Red |
|
2 |
D- |
White |
|
3 |
D+ |
Green |
|
4 |
GND |
Black |
|
5 |
StdA_SSTX- |
Blue |
|
6 |
StdA_SSTX+ |
Yellow |
|
7 |
GND_DRAIN |
GROUND |
|
8 |
StdA_SSRX- |
Purple |
|
9 |
StdA_SSRX+ |
Orange |
|
Shell |
Shield |
Connector
Shell |
|
|
The USB 3.0
specification also includes new power management features including
support for idle, sleep, and suspend states, as well as Link-, Device-,
and Function-level power management. The bus power spec has also been
increased to 900mA, an 80% increase over USB 2.0 (500mA).
With the USB
3.0 specification completed and released in 2008, many desktop and
notebook motherboard manufacturers such as Gigabyte and Intel either
have plans to or have already integrated the latest SuperSpeed USB 3.0
ports into their hardware. It is expected that by the year 2012, over 4
billion USB 3.0 devices will have been shipped.
Transfer rate comparison of USB 2.0 and USB 3.0
Below is a
comparison showing the difference in transfer rate between a USB 2.0
port and USB 3.0 port. Taking a look at the sequential Read / Write
performance of the SATA drives connected to the USB 2.0 port, we find
that even a single 3.5" SATA hard drive will saturate the bandwidth of
the USB 2.0 port. On the other hand, there is a significant improvement
in performance when comparing a single 3.5" SATA hard drive and a three
SATA drive RAID 0 set. In fact, even the three SATA drive RAID 0 set has
not yet saturated the USB 3.0 bus.
|
1TB
3.5” Seagate SATA HDD connected to
USB 2.0 port on Gigabyte motherboard |
1TB 3.5” Seagate SATA HDD connected to
Addonics 2-Port USB 3.0 PCI-Express 1X Controller |
 |
 |
|
3 Drive RAID 0 set
connected to
USB 2.0 port on Gigabyte motherboard |
3 Drive RAID 0 set
connected to
Addonics 2-Port USB 3.0 PCI-Express 1X Controller |
 |
 |
|
