▮ The differences between USB4.0 and USB3.2
1. Broadband transmission
USB3.2 Max is 20Gbps (USB3.2×2 Max is 40Gbps) and USB4 Max is 40Gbps.
2. transport protocols
USB 3.2 Transfers data through the USB protocol, or configures USB and DP using DP Alt Mode(alternative Mode). USB4 encapsulates USB 3.2, DP, and PCIe protocols into packets through tunneling technology and sends them at the same time.
3. The transmission of the DP
Both support DP 1.4. USB 3.2 Use DP Alt Mode(alternative Mode) to configure output. The USB4 can not only configure the output by DP Alt Mode(alternative Mode) but also extract DP data through the USB4 tunnel protocol packet.
4. The PCIe transmission
USB 3.2 does not support PCIe. USB 4 supports PCIe only. PCIe data is extracted through the USB4 tunnel protocol packets.
5. TBT3 transmission
USB 3.2 does not. USB 4 does. That is, it extracts PCIe and DP data through the USB 4 tunnel protocol packets.
6. Host to Host
Communication between hosts is not supported by USB 3.2 but is supported by USB 4. This function is supported only when the USB 4 supports PCIe.
7. USB4.0 Feature
The USB4™ Tunneling architecture packages the USB3 / DisplayPort™/ PCI Express on the same interface for transmission, and the bandwidth allocation of each protocol can be dynamically adjusted.
8. USB4.0 optional function
The USB4™ is optional for TBT3 system compatibility.
Remark: Tunneling technology can be regarded as a technology that integrates data from different protocols, and the types are distinguished by packet headers.
USB 3.2 allows DisplayPort video and USB 3.2 data to be carried on different channel adapters, while USB4 allows DisplayPort video, USB 3.2 data, and PCIe data to be carried on the same channel, which is the major difference between the two.
From the above features, it is easy to see that the logical architecture of USB4™ is very similar to the network architecture. The various protocol packets are carried by a fixed frame and physical layer, which may contain data and image packets, and each packet is tagged with an address to ensure correct transmission. As a result, USB4™ moves away from the limitations of traditional USB host and USB device functionality by using point-to-point transmission. This design retains great flexibility to further improve transmission speed and functionality in the future.
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