M1 电脑的雷雳接口也是 USB4 接口，USB4 其实就是 Mandated USB-C + Optional TB3。苹果官网告诉我们 M1 的雷雳控制器是苹果自己设计的，应该是整合在 M1 上面了，因为拆机发现 m1 距离接口的位置有两个 retimer，Thunderbolt is very sensitive to trace distances.
It’s always about the trade-offs. Intel offered two controllers up until recently. A one-port bus controller, and a two-port bus controller. Since the controllers needed to be very close to the ports, and aren’t exactly small, Apple opted for the two-port bus controllers. It saves space on the logic board, and only requires 4x PCIe lanes to feed it, so you aren’t fighting for I/O from the CPU that is also needed for the 5300M in the 16” MBP.
They could have done 1-port-per-bus under Intel. They just decided not to. But the 16” MBP logic board looks pretty crammed as it is, so I’m not terribly surprised here.
Moving to Apple Silicon gives them more options. They don’t have to ration PCIe lanes if they don’t want to. Their GPU design may give them the ability to free up lanes and I/O that would normally go to a dGPU in the 16” MBP. But there’s still the trade offs. 4 integrated controllers means 4 retimers and more I/O pins dedicated to it. There are advantages to this, but my use of TB doesn’t really benefit from it. About the only devices capable of saturating TB are PCIe SSDs, some RAIDs, and eGPUs. With DSC in the mix now, high resolution displays going forward will likely use less bandwidth than the LG 5K Ultrafine. It depends a bit on how common SSDs and RAIDs are in pro workflows, I bet.
The question really winds up being: What does Apple think Pros want/need? What trade offs in the “M1X” design are they willing to make to cater to that vision? I’m honestly not very sure how this will play out. Apple certainly has data on how the four port MacBook Pros get used, and I kinda wish I had access to it.