McPAT-Monolithic: An Area/Power/Timing Architecture Modeling Framework for 3-D Hybrid Monolithic Multicore Systems

Three-dimensional integrated circuits (3-D ICs) have the potential to push Moore's law further by accommodating more transistors per unit footprint area along with a reduction in power consumption, interconnect length, and the number of repeaters. Monolithic 3-D integration is particularly promising in this regard as it offers a very high connectivity between vertical transistor layers owing to its nanoscale monolithic intertier vias. Monolithic integration can be realized at block-, gate-, and transistor-level granularity. A hybrid monolithic (HM) design aims to further optimize area, power, and performance of the chip by combining different monolithic styles. In this article, we introduce McPAT-monolithic, a framework for modeling HM multicore architectures. We use the OpenSPARC T2 processor as a case study to compare different monolithic implementation styles and explore the benefits of HM design. Our simulations show that, under the same timing constraint, an HM design offers 47.2% reduction in footprint area and 5.3% in power consumption compared to a 2-D design at the cost of slightly higher on-chip temperature.