Energy per bit (pJ/bit)
Beginner
How much energy it takes to send one bit, a single 1 or 0, across a link. Less energy per bit means a cooler, cheaper link.
Novice
The energy a link spends per transferred bit, in picojoules ( joules). Power in watts = bits per second × joules per bit, so 1 Tb/s at 1 pJ/bit costs 1 W.
Expert
Covers transmitter, receiver, clocking and the wire’s capacitance; shorter, finer wires need less. Targets fall from about 0.5 pJ/b on an organic substrate to 0.25 on an interposer and under 0.05 with hybrid bonding; SerDes built to cross a circuit board spend far more.