RE: [SI-LIST] : An Interesting Presentation

Magnus Homann (
Wed, 21 Apr 1999 15:06:02 +0200

Hello SI-list!
> > On the other hand, I don't see why Ethernet is necessarily any more
> > difficult than, say, RAMBUS, despite having 40 times the "difficulty"
> > metric. Nor why it is 1600 times more difficult than 66MHz PCI! It seems
> > to me that the things that determined Ethernet's need for special low
> > capacitance receivers and such, were the electrical constraints, NOT
> > timing. So I completely disagree with Dr. Johnson's choice of examples.
> > These are cases where the electrical considerations far outweigh the
> > simple timing needs, and in my mind they make Howard Johnson's
> > presentation fall apart.

What differs between PCI and Ethernet is basically that in ethernet the
clock travels with the data, so that sender and receiver have different
clocks. Clock periods isn't then the relevant measure on how much time
you have to spare. Not so in PCI.

Just a few thoughts,

Magnus Homann
Ericsson Mobile Data Design AB

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