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This is definitely a dumb question (no background in signal processing), but what types of use cases are there for lines > 100MHz? I'm assuming a lot (maybe most?).

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Mar 26·edited Mar 26Author

They're used whenever you need to move a lot of data real fast. Typical examples might be the bus between RAM and the CPU on a PC motherboard, an HDMI connection to a monitor, or something like an external drive inserted into a USB 3.0 port.

As a general rule, these signals are challenging to deal with even on a PCB, but they're particularly tricky if you need connectors and cables running some distance. This is why high-speed cables tend to be a lot more intricate than we assume - for example, here's HDMI:

https://i.redd.it/f5ewym0r4oka1.jpg

All this to minimize impedance between differential pairs, reduce cross-talk, and keep EMI in check.

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Interfaces / Interconnects like PCIe, High Speed ADCs, reference clocks, etc?

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