We investigate coding techniques to reduce the energy consumed by on-chip buses in a microprocessor. We explore several simple coding schemes and simulate them using a modified SimpleScalar simulator and SPEC benchmarks. We show an average of 35% savings in transitions on internal buses. To quantify actual power savings, we design a dictionary based encoder/decoder circuit in a 0.13µm process, extract it as a netlist, and simulate its behavior under SPICE. Utilizing a realistic wire model with repeaters, we show that we can break even at median wire length scales of less than 11.5mm at 0.13µ and project a break-even point of 2.7mm for a larger design at 0.07µ.