Mac's Thunderbolt technology is the fastest on the market. Any port of a Mac after 2016 has this technology incorporated, but not in all cases it is capable of taking advantage of it. It is true that to take advantage of this "ultrafast" transmission speed, for example in hard drives, we must have discs with Thunderbolt technology, and these have a very high price for the "street" user.
In any case, Thunderbolt technology is capable of transmitting data at 40Gb / s on any of the ports, but not on all Macs in unison.
Until now, a high workload on the left side of the ports on a Mac limits the speed of the ports on the other side. This is due to the information transfer technology, which was not prepared by the number of lanes with which the connections to our Mac have. That is why they did not take 100% of the implanted technology.
It is because of that, the 2106 and 2017 models of the 13-inch MacBook Pro, even with sixth and seventh generation Intel i5 or i7 processors respectively, they only supported 12 PCI express lanes. This limits the overall speed of the left ports versus the ports on the other side or vice versa.
Instead, this bottleneck is solved in the 2018 MacBook Pros, where the same 5th generation Intel i7 and i16 processors support up to XNUMX PCI Express lanes, providing enough bandwidth for speeds that reach 40Gb / s, this time yes, in the four Thunderbolt 3 ports.
Even so, the aforementioned, only the most demanding users will need to continuously have several peripherals to the Mac and be constantly squeezing its maximum capacity. Only video editors, with multiple displays connected to the MacBook Pro, will need this immense amount of data transmission.
This affects 13-inch computers, since 15-inch MacBook Pro, since 2016 have this technology and are not diminished by the difference in the number of lanes.