TidBITS posted a very interested find:
Thunderbolt Improvements in the M1-Based Macs:
…the new Macs have only two Thunderbolt ports, compared to four on the Intel-based 13-inch MacBook Pro and Mac mini, [SoftRAID developer Tim] Standing discovered that each port has its own Thunderbolt bus.
By comparison, each pair of Thunderbolt ports on the Intel-based Macs share a bus, meaning that they also share bandwidth. If you plug two fast drives into ports that share a bus, performance suffers.
Standing also notes that the M1-based Macs have Thunderbolt 4, which differs from Apple’s implementation of Thunderbolt 3 in only one fundamental way: Thunderbolt 4 adds support for Thunderbolt hubs that let you add more ports.
To read the original article (linked from TidBITS) go here:
Thunderbolt on the M1 Mac mini – When 2 Actually Does Equal 4