Why transition coding for power minimization of on-chip buses does not work

Encoding techniques which minimize the self- or coupling activity of buses are often proposed to reduce power dissipation on system buses. In this paper, we investigate the efficiency of several coding schemes for on-chip buses with respect to overall power dissipation. The power of the codec systems was estimated by power simulations with the lay-outs and related to the savings on the bus. We derived an expression for the energy efficiency of the codecs as a function of bus length (capacitive load). Despite the fact that adaptive schemes could obtain up to 40% savings, the bus lengths required to reduce the overall power consumption are not realistic for on-chip buses.