Impact of Small Process Geometries on Microarchitectures in Systems on a Chip

Process effects in deep-submicrometer geometries are expected to change the physical organization, or microarchitecture, of integrated circuits. The factor that is expected to primarily impact integrated circuit microarchitectures is increasing delays in interconnect. We believe that, to properly microarchitect integrated circuits in small process geometries, it is necessary to get as detailed a picture as possible of the effects and then to draw conclusions about changes in microarchitecture. To this end, in this paper, we describe a comprehensive approach to accurately characterizing the device and interconnect characteristics of present and future process generations. This approach uses a detailed extrapolation of future process technologies to obtain a realistic view of the future of circuit design. We then proceed to quantify the precise impact of interconnect, including dynamic delay due to noise, on the performance of high-end integrated circuit designs. Having determined this, we then reconsider the impact of future processes on integrated-circuit design methodology. We determine that local interconnect effects can be managed through a deep-submicrometer design hierarchy that uses 50K–100K gate modules as primitive building blocks. In light of this new system-on-a-chip microarchitecture, we then examine global interconnect issues. Our results indicate that, while global communication speeds will necessarily be lower than local clock speeds, International Technology Roadmap for Semiconductors expectations should be attainable to the 0.05m technology generation. Achieving these high clock speeds (10 GHz local clock) will be aided by the use of a newly proposed routing hierarchy that limits interconnect effects at each level of a design (local, isochronous, and global). In addition, key components of the interconnect architecture of the future include fat (or unscaled) global wires, intelligent repeater and shield wire insertion, and efficient packaging technologies.