Now I don't happen to agree with 'userbinator's skepticism -- indeed I think that a lot of engineers who work with digital stuff tend to forget that it is analog under the hood, with all the associated crosstalk and BER problems. But creating this atmosphere of "Ooooooh, it is something you probably don't understand" isn't very productive, if you know what I mean. I wish Johnson had titled his books, "High-Speed Digital Design: Quite Simple If You Do the Math and Physics".