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1. niconiconi (niconiconi@cybre.space)'s status on Wednesday, 20-Apr-2022 17:21:38 UTC niconiconi

   Therapist: Complex impedance is not real, it can't hurt you.

   Complex impedance: an open circuit with nothing connected automagically becomes a short circuit when the signal line is at quarter wavelength.

   Digital designers: AAAAAAAAAAAAAAAAAA

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   • niconiconi (niconiconi@cybre.space)'s status on Thursday, 21-Apr-2022 01:17:12 UTC niconiconi

     in reply to

     • Vertigo #$FF

     @vertigo In modern digital systems the bus itself is often not the problem, in point-to-point series links with on-die impedance termination on both sides, it doesn't matter.

     The data rate has increased to the point when the PCB vias are the problem, e.g. if you change from layer 1 to layer 4 with a via, the open-ended portion of that via at layer 5 and 6 becomes a short circuit at quarter wavelength, at this frequency the cable is shorted and the loss is infinite, at 20 Gbps+ this is a serious problem... For advanced board, blind vias and backdrilling are almost essential.

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   • Vertigo #$FF (vertigo@hackers.town)'s status on Thursday, 21-Apr-2022 01:17:13 UTC Vertigo #$FF

     in reply to

     @niconiconi I honestly forgot about that. But, that's an outstanding thing to remember, especially if one is designing expansion ports!

   • SeTec Astronomy :blobbandage: (setecastronomy@hackers.town)'s status on Thursday, 21-Apr-2022 01:17:32 UTC SeTec Astronomy :blobbandage:

     in reply to

     • Vertigo #$FF

     @niconiconi @vertigo You all make me glad I'm still trying to make basic TTL stuff work on a breadboard.

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