USB 3.0 General Description and Comparison of USB 3.0 to USB 2.0

apatro — Thu, 07 Oct 2021 04:43:21 GMT

Current Revision posted to Documents by apatro on 10/7/2021 4:43:21 AM

Initially, USB provided two speeds (1.5 Mb/s and 12 Mb/s). As PCs became increasingly powerful and able to process larger amounts of data, users needed to get more and more data into and out their PCs. This led to the definition of USB 2.0 specification to provide a transfer rate of 480 Mb/s while retaining backward compatibility.

As technology innovation marches forward, new kinds of devices, media formats, and large inexpensive storage are converging. They require significantly more bus bandwidth to maintain the interactive experience users have come to expect. In addition, user applications demand a higher performance connection between the PC and these increasingly sophisticated peripherals. USB 3.0 SuperSpeed addresses this need by adding an even higher transfer rate to match these new usage and devices.

SuperSpeed USB 3.0 supports a maximum data rate of 4.8 gigabits per second offering 10x performance increase over Hi-Speed USB (USB 2.0)
USB 3.0 is full duplex, meaning it can upload and download simultaneously (it's bi-directional); USB 2.0 is only half duplex
Backwards compatibility with USB 2.0 hi-speed devices
USB 3.0 has got dual bus architecture means SuperSpeed bus operates concurrently with USB 2.0
SuperSpeed USB is a Sync-N-Go technology that minimizes user wait-time.
SuperSpeed USB will provide improved power efficiency. No device polling and lower active and idle power requirements
USB 3.0 SuperSpeed creates a communication pipeline with host and each device or a "host-directed protocol". The older USB 2.0 Hi-Speed broadcasted packets to all devices.
Cable makeup: 2 wires for power and ground, 2 for Hi-Speed backward compatibility, 4 wires for the new Superspeed
Shielded differential pair (SDP, twisted or twinax) is needed for USB 3.0. UTP cable used for USB 2.0 can not be used for USB 3.0
USB 3.0 cable can be upto 3 meters to maintain SuperSpeed data transfer rates
USB 3.0 SuperSpeed can handle more power over its cable. 50% more than USB 2.0
USB 3.0 has dual simplex and asynchronous notifications
USB 3.0 Standard-A connector has complete compatibility with USB 2.0 Standard-A connector. However, a new receptacle has been created "USB 3.0 Standard-B" which can only accept a USB 3.0 Standard-B device plug.

Fig: USB 3.0 Standard-A Connector

Comparison of USB 3.0 to USB 2.0

Features	USB 3.0	USB 2.0
Speed	Upto 4.8 Gb/s	upto 480 Mb/s
Signaling	Dual-simplex four wire differential signaling	Two wire differential signaling
Data flow	Full duplex	Half duplex
Power Management	Multi-level which supports idle, sleep, and suspend	Port-level that has two levels of entry/exit latency
Cable types	Shielded differential pair (SDP)	Unshielded twisted pair (UTP)
Cable Wires	8 total	4 total
Traffic Flow	Asynchronous	Polled
Packet Traffic	Explicitly routed	Broadcast to all devices