What is the difference between USB4.0 and USB3.2?

What is the difference between USB4.0 and USB3.2?

What is the difference between USB4.0 and USB3.2?

Before introducing USB4, we have to mention the Thunderbolt protocol launched by Intel and Apple.

Thunderbolt protocol is a combination protocol that integrates DisplayPort protocol (DP for short) and PCI-Express protocol (PCIe for short).

The Raiden 1 and Raiden 2 protocols have been launched successively, but the response has been mediocre.

Later, the Thunderbolt 3 protocol (TBT3 for short) was launched, and the transmission speed reached 40Gbps. Later, Intel chose to hand over the protocol to the USB-IF Association.

In 2019, USB-IF integrated the Thunderbolt 3 protocol (TBT3 for short) on the basis of USB 3.2, and launched USB4 Gen 2×2 and USB4 Gen 3×2.

The difference between this name change and the past is that the name of USB 3.2 is still retained.

USB4 has doubled the transmission speed of the original USB 3.2, reaching 40Gbps, which is the speed of USB4 Gen 3×2. USB4 supports both USB 3.2 and TBT3 transmission.

In short, USB4=USB 3.2 TBT3.

Like USB 3.2, USB4 also has single-channel mode and dual-channel mode. The USB4 interface, like the USB 3.2 interface, supports the USB PD fast charging protocol.

Both USB4 and USB3 use type-C port

USB-C, the full name of USB Type-C, is a physical appearance of the USB interface (remember to test it), light and thin, no need to distinguish the front and back, and supports front and back blind insertion.

It has 24 pins, which can accommodate almost all USB transmission protocols, including USB2.0, USB3.0, USB 3.2, USB4, etc., as well as USB-PD fast charging protocol, DisplayPortP digital video protocol, Thunderbolt 3/4 protocol, etc. , so as to achieve higher USB transmission speed, power supply potential up to 100W and performance potential for transmitting ultra-clear video signals, there is a tendency to unify the interface.

As mentioned earlier, USB Type-C is just a physical form of the interface, and the actual performance depends on which protocol it uses.

What is USB4?

USB4 is a protocol for transferring data. It adopts the physical form of USB-C and integrates the Thunderbolt 3 protocol, while supporting high-speed data transfer and video/audio transfer. Its main performance is as follows:

1. Divided into two versions: USB4 20 (theoretical rate 20Gbps) and USB4 40 (theoretical rate 40Gbps);

2. Compatible with DisplayPort 2.0 video transmission protocol, support real-time transmission of 8K@60Hz+HDR10 video;

3. You can connect an external graphics card, two 4K monitors or one 5K monitor, etc.

4. Supports up to 100W PD power supply, covering the charging power of most devices;

The USB4 developed based on the Thunderbolt 3 protocol has stronger versatility, lower device requirements, no licensing fee, and is backward compatible with various USB standards and Thunderbolt 3, and is complementary and compatible with Thunderbolt 4.

What is the difference between USB4.0 and USB3.2?

1. Transmission bandwidth: 

USB 3.2 has a maximum of 20Gbps (USB3.2X2 has a maximum of 40Gbps), while USB4 has a maximum of 40Gbps.

2. Transmission protocol:

USB 3.2 mainly transmits data through USB protocol, or configures USB and DP through DP Alt Mode (alternative mode).

And USB4 encapsulates USB 3.2, DP and PCIe protocols into data packets through tunneling technology and sends them at the same time.

3, DP transmission:

can support DP 1.4. USB 3.2 configures output through DP Alt Mode (alternative mode); while USB4 can not only configure output through DP Alt Mode (alternative mode), but also extract DP data through USB4 tunnel protocol packets.

4. PCIe transmission:

USB 3.2 does not support PCIe, but only USB4. PCIe data is extracted through USB4 tunnel protocol packets.

5. Transmission of TBT3:

USB 3.2 is not supported, but USB4 is supported, that is, to extract PCIe and DP data through USB4 tunnel protocol packets.

6. Host to Host:

Communication between host and host, USB3.2 does not support, USB4 supports. Mainly USB4 supports PCIe protocol to support this function.

7. USB4™

• The USB4™ Tunneling architecture packages USB3 / DisplayPort™ / PCI Express in the same interface for transmission, and the bandwidth allocation of each protocol can be dynamically adjusted.
• USB4™ can choose whether it is compatible with the TBT3 system.
• USB4™ supports Host to Host (host and host). Host docking transmission signal)

Note: Tunnel technology can be regarded as a technology that integrates data of different protocols, and the types are distinguished by the data packet header.

In USB 3.2, DisplayPort video and USB 3.2 data are transmitted in different channel adapters, while in USB4, DisplayPort video, USB 3.2 data and PCIe data can be transmitted in the same channel, which is the biggest difference between the two .

From the above characteristics, it is not difficult to find that the logical architecture of USB4™ is very similar to the network architecture.

Carrying different protocol packets in a fixed frame and physical layer, which can include data and image packets, and marking each packet with an address to ensure correct transmission.

Therefore, USB4™ gradually gets rid of the functional limitations of traditional USB Host and USB Device, and USB4™ uses point-to-point transmission.

This design reserves great flexibility for improving the transmission speed and function in the future.