USB 2.0 vs. USB3.0

USB 3.0 provides better speed and more efficient power management than USB 2.0 . USB 3.0 is backwards compatible with USB 2.0 devices; however, data transfer speeds are limited to USB 2.0 levels when these devices are interfacing. In 2014, a new standard, USB 3.1 , was released and is expected to be in widespread use by 2015.

Comparative graph

USB 2.0 vs. USB 3.0 Comparison Chart

USB2.0	USB3.0


Published	April 2000	November 2008
Speed	High speed or HS, 480 Mbps (Megabits per second)	10 times faster than USB 2.0. Super Speed or SS, 4.8 Gbps (Giga bits per second)
Signaling method	The polling mechanism, i.e. can send or receive data (Half duplex)	Asynchronous mechanism, i.e. can send and receive data simultaneously (full duplex)
Price	For a similar product, the USB 2.0 version is generally less expensive than the USB 3.0 version.	For a similar product, the USB 3.0 version is generally more expensive than its USB 2.0 version.
Energy consumption	up to 500mA	Up to 900mA. Allows better power efficiency with less power for idle states. You can power more devices from one hub.
Number of wires inside the cable	4	9
Standard connectors A	Gray	Color blue
Standard-B Connectors	smaller in size	Extra space for more cables.
cable length	5 meters	3 meters

Content: USB 2.0 vs USB 3.0

1 What is USB 3.0 and USB 2.0?
- 1.1 What is USB 3.1?
2 Highlights and advantages of USB 3.0 over USB 2.0
3 physical differences
4 Backwards compatible
5 price
6 references

What is USB 3.0 and USB 2.0?

A USB 3.0 stick

Developed in the 1990s, the Universal Serial Bus (USB) standard was developed to define communication protocols, including cables and connectors, between computers and electronic devices such as printers and scanners. As the number of devices multiplied in number and types, the USB port was adopted as the basic connection portal.

Devices such as smartphones, PDAs, tablets, smartphones, and video game consoles can be connected to computers with USB ports, allowing recharging and communication, thus replacing the requirement for power adapters and chargers.

USB3.0 was released in November 2008, almost eight years after the release of USB 2.0. More than five years later, in 2014, USB 3.1 was released with widespread use expected in 2015.

What is USB3.1?

The new standard is for USB 3.1 USBs. It offers three major improvements over 3.0: an “always right” Type-C connector that plugs in regardless of orientation, higher data transfer speeds of up to 10 Gbps (gigabits per second), and the ability to power any type of device. .

The Type-C connector is small enough for modern, slim devices such as MacBook Air-style laptops, tablets, and smartphones. But still robust enough for 10,000 cycles of use. Data transfer speeds are more in sync with the current application and user needs, especially for video and image files. And the option to plug in and power any type of device, with 100 watts of charging power that can be split between two devices, greatly reduces “charger and cable clutter,” simplifying connectivity between personal devices. However, backwards compatibility will be limited.

Highlights and benefits of USB 3.0 over USB 2.0

Transfer rates: USB 2.0 offers transfer rates of 480 Mbps, and USB 3.0 offers transfer rates of 4.8 Gbps, 10 times faster.

Adding another physical bus: The number of cables was doubled from 4 to 8. The additional cables required more space in both cables and connectors, so new types of connectors were designed.

Power consumption: USB 2.0 provides up to 500mA, while USB 3.0 provides up to 900mA. USB 3 devices provide more power when needed and conserve power when the device is connected but idle.

More Bandwidth: Instead of one-way communication, USB 3.0 uses two one-way data paths, one for receiving data and the other for transmitting, whereas USB 2.0 can only handle one direction of data at any one time.

Improved bus utilization: Added a new feature (using the NRDY and ERDY packages) to allow a device to asynchronously notify the host of its availability.

When data is transferred through USB 3.0 devices, cables, and connectors, the transaction begins when the host makes a request followed by a response from the device. The device accepts the request or rejects it. If accepted, the device sends data or accepts data from the host. If there is no space or data in the buffer, it responds with a Not Ready (NRDY) signal to indicate to the host that it cannot process the request. When the device is ready, it will send an Endpoint Ready (ERDY) to the host, which will then reschedule the transaction.

physical differences

USB 3.0 connectors are different from USB 2.0 connectors, and 3.0 connectors are usually colored blue on the inside to distinguish them from 2.0 connectors.

Various types of USB connectors (click to enlarge). From left to right: Micro USB Type AB, Micro USB Type B, USB 2.0 Type A, USB 2.0 Type B, USB 3.0 Type A, USB 3.0 Type B, USB 3.0 Type Micro B, Min USB Type A connector

Backward Compatible

USB 3.0 is backwards compatible with USB 2.0. However, the USB 3.0 product will perform at the same level as a USB 2.0 product, so the speed and power benefits will not be fully realized.

USB 3.0 receptacles are electrically compatible with standard USB 2.0 device plugs if they physically match. USB 3.0 Type A plugs and receptacles are fully backward compatible, and USB 3.0 Type B receptacles will accept USB 2.0 and earlier plugs. However, USB 3.0 Type B plugs will not fit into USB 2.0 and earlier receptacles.

This means that USB 3.0 cables cannot be used with USB 2.0 and USB 1.1 peripherals, although USB 2.0 cables can be used with USB 3.0 devices, if they are at USB 2.0 speeds.

The following videos review the speed of USB 2.0 vs USB 3.0 products:

Speed test for eSATA USB 3.0 vs 2.0
Kingston HyperX Max 64GB SSD Speed Test

Price

For a similar product, the USB 3.0 version is generally more expensive than its USB 2.0 version.

You can check the current prices on Amazon for some USB 2.0 vs USB 3.0 enabled devices:

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USB 3.0 Compliant Products
USB 2.0 Compliant Products

References

Universal Serial Bus Overview – Intel
USB 3.0 Super Speeds – USRobotics
USB 3.1 and its disruptive USB Type-C connector – Tom’s Hardware
Wikipedia: USB 3.0
Wikipedia:USB