The single most important idea in modern connectivity is that the cable stopped carrying one protocol and started carrying a switchable fabric. How USB4 and Thunderbolt tunnel PCIe, DisplayPort, and USB3 over the same wire, the router-and-adapter architecture underneath, PAM3 and the 120Gbps asymmetric trick, the DMA security problem, and why the USB-C port is a lie.
Thunderbolt
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Thunderbolt and USB4: How Tunneling Actually Works