Thunderbolt 4 was announced in 2020, and its final specifications were published in July of 2020. The main distinctions in Thunderbolt 4 and Thunderbolt 3 include the minimum bandwidth requirement of 32 Gbit/s on PCIe links and compatibility with dual display 4K, and Intel's VT-D-based Direct Memory Access protection that blocks physical DMA attacks.
Another significant enhancement has been that Thunderbolt 4 now supports Thunderbolt Alternate Mode USB hubs ("Multi-port Accessory Architecture") as well as not only daisy-chaining.
These hubs are backwards and compatible Thunderbolt 3 devices and can be backwards compatible with Thunderbolt 3 hosts. You can also buy thunderbolt 3 and 4 via an online Thunderbolt store.
The maximum speed is 40 Gbit/s. This is the same as Thunderbolt 3 and 4 times more efficient over USB 3.2 Gen2x1.Supporting devices began coming in the second quarter of 2020 and include Tiger Lake mobile processors for Project Athena notebooks and 8000 series independent Thunderbolt controllers.
DisplayPort Alt Mode 2.0: USB4 supports DisplayPort 2.0 over the alternative mode. DisplayPort 2.0 supports higher than eight-inch resolution at 60 Hz without loss thanks to the brand newly developed UHBR 10.3, 13.5 20 and 13.5 signaling specifications (DSC 1.2 that is used for DisplayPort 1.4) .
The maximum of 80 Gbit/s which is more than double the data that is available to USB data because (just like in DisplayPort 1.4) DisplayPort 2.0 can send nearly all data in only one direction (to the monitor) and is able to utilize all eight data lanes at the same time.