Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

[BP] Relationship to cabling standards

I believe there are important differences between the emerging 802.3ap standard and existing cabling standards.
  1. Cable, by its physical nature, does not have the potential to have stubs.
  2. Cable manufacturers are further prevented from creating ill-behaving electrical channels via the existence of cabling standards.
  3. The variation in electrical characteristics of cables will be very small compared to the electrical variations in the universe of backplanes.  Consequently, the problem space for cable channels is very narrow while the problem space for backplane channels is very wide, and has more dimensions.
  4. A particular implementation is not difficult to design signaling for, it's the huge universe of bad and weird channels that causes the problem for signaling.  Each one may represent 1% of the market, but putting an operating envelope around ALL of them is what is going to cost the industry in terms of die area, power, time to market and widescale availability.
  5. We are expecting to see the number of 802.3ap transceivers-per-IC sometimes appoach 100 transceivers.  The "costs" mentioned above will be multiplied by this number.  What might have been done for something like 1000BaseT, where a couple transceivers/IC might be seen, is not appropriate here.
BrianS