The latest versions of USB and PCIe are no longer binary digital signalling at all. It is a modulated radio signal [1] carried over a wire, similar to how DSL

The latest versions of USB and PCIe are no longer binary digital signalling at all. It is a modulated radio signal [1] carried over a wire, similar to how DSL and cable modems work. Processor and memory busses will be next to switch over. Most digital systems will probably move in this direction as speeds continue to increase. [1] https://en.wikipedia.org/wiki/Pulse-amplitude_modulation https://en.wikipedia.org/wiki/Pulse-amplitude_modulation