Haar-based interconnect coding for energy effective medium/long range data transport

In this paper we introduce and evaluate Haar based codec assisted medium and long range data transport structures, e.g., bus segments, Network on Chip interconnects, able to deal with technology scaling related phenomena (e.g., increased susceptibility to proximity coupling noise and transmission delay variability), targeting energy savings at the expense of a reasonably small overhead, i.e., 1 extra wire, a 2-gate encoder, and a 2-gate decoder, for each and every pair of uncoded wires. For practical evaluation we employed a 45nm commercial CMOS technology and different random, uncorrelated workload profiles. For 5mm and 10mm long 8-bit buses (without repeaters), we obtain energy savings of 55% and 34%, and a transmission frequency increase of 35% and 41%, respectively, at the expense of less than 1% area overhead with respect to the reference system (i.e., 8-wire synchronous uncoded bus), which prove energy and delay effectiveness. We further augment our proposal with a Single Error Correction and Double Error Detection (SECDED) scheme particularly adapted to its structure, in order to cope with very deep sub-micron noise (e.g., supply voltage variations, electromagnetic interference) induced transmission errors. When compared to the reference system (not SECDED protected), for 10mm long buses, our Haar tailored SECDED approach consumes 27% less energy at the expense of 2% area overhead.