Richard,

Just a few words about modeling. Yes, they built a model of a 4004 before
they made the chip. They stopped doing that somewhere around the 386.

As for my analog simulation, the simulator I am using is distributed by
Linear Technology Inc so that people can model circuits using their chips. A
lot of real world stuff is sort of simulated, where an analog signal is
digitized, and all filtering and other audio stuff is actually done in a
DSP.

If you want to see something that will really blow your mind, check out the
Harris digital AM transmitter; and no, I don't mean a transmitter for
digital audio.

Tam/WB2TT