In this talk, we’ll see how crosstalk, ISI (inter-symbol interference), FEC (forward error correction), and equalization have driven high speed IO away from NRZ (which should be PAM2–2-level pulse amplitude modulation) to the madness of PAM4, PAM5, PAM6, PAM-fried engineers. Along the way, we’ll investigate how simple, righteous design constraints have evolved to arbitrarily complicated figures of merit like malicious COM (channel operating margin) and evil ERL (effective return loss) by standards committees intent on world domination. It’s a sad tale, guaranteed to keep engineers employed.
