You can determine whether Thunderbolt 3 or Thunderbolt 4 is based on the following methods:
Video transmission support. The interface of Thunderbolt 4 can be connected to at least two 4K monitors, or one 8K monitor, while Thunderbolt 3 can only support one 4K monitor at most.
PCIe data transfer speed. Thunderbolt 4's PCIe data transmission speed certification starting point is 32Gbps, which is equivalent to the speed of PCIe3.0x4, while the Thunderbolt 3 interface requires at least 16Gbps.
safety. The Thunderbolt 4 interface adds direct memory access (DMA) protection based on Intel VT-d in the certification, which can avoid physical DMA attacks and improve security.
Sleep wake-up function. The Thunderbolt 4 interface supports waking the computer from sleep state through an external keyboard and mouse, while the Thunderbolt 3 interface does not support this function.
Interface identification. If the Type-C interface supports the Thunderbolt protocol, the lightning mark must have a small triangular arrow. If the Thunderbolt 4 protocol is supported, it is usually marked with the word "4" next to the lightning mark with a small triangular arrow.
