people say things like "breadboards are 10 MHz max" (basically true) from which they derive conclusions like "pin headers, which have the same pitch as a breadboard, are 10 MHz max" which are entirely false. although you do need to treat it like a transmission line above ~20 MHz or nothing will work
@whitequark✧✦Catherine✦✧ My favourite example of a connector that does. not. look high speed, is probably the subconn DBH13M. Good for gigabit ethernet (and separate power!), just remember to lube it up well first
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