(Original Question: I have a Mac Pro with thunderbolt3 port. Can I use the new thunderbolt4 Qnap with that ? Is there an advantage to this )
Yes, you can indeed connect a Thunderbolt 4 device to a Thunderbolt 3 host, such as your Mac Pro. There is complete backward compatibility between Thunderbolt 3 and Thunderbolt 4, allowing Thunderbolt 3 devices to connect to a Thunderbolt 4 host. This works the other way round too - a thunderbolt3 device can connect to a thunderbolt4 host too.
Regarding the advantage of this connection, as there's no difference in the maximum transfer rate between Thunderbolt 3 and Thunderbolt 4, the key distinction lies in the minimum guaranteed transfer rate. Thunderbolt 4 ensures a minimum transfer rate of 40Gbps, while Thunderbolt 3 can achieve either 20Gbps or 40Gbps. However, given that your host is Thunderbolt 3, the likelihood of achieving the full 40Gbps transfer rate on a Thunderbolt 4 device is low. Therefore, you may not experience the complete advantage of the enhanced transfer rate.
I trust this answers your question. If you have queries or need clarification, please don't hesitate to reach out or use the comments section to engage.