3 ms·

I think those are two different demos, years apart (1995 vs 1998)? You're right that it's sure not clear.

• mindslight 2y ago
  Ah, I had missed the author's caption on that photo dating it at 1998. Looking at it again, it's even more odd because the article was written in 2001 - meaning that the 100Base-T4 anecdote was twice as old as the gigabit demo photo. The part that stands out to me is the author writing off the high frequency loss because each pair is only carrying 25 mbit, yet Gigabit is ten times the bandwidth which is around where I'd think things would start to get a bit wonky. But maybe my intuition is still just the result of single conductor flapping around in free space, rather than a "controlled" impedance balanced pair.
  • exmadscientist 2y ago
    Gigabit brings in all four pairs, so it's only at 125 MHz, five times faster (which is in fact exactly why it does that). That's not all that much worse than 25 MHz. And as for intuition... Howard Johnson is something of the authority on signal propagation, so if he says that's what your intuition ought to be, I listen!
    • mindslight 2y ago
      I'm just saying, scopes have a 20Mhz limiting switch for a reason and that's also around where I start to think something might be better off not on a breadboard. I recognize neither of those things is a controlled impedance pair. It just hits differently to write off 25MHz vs 125MHz as "low frequency".