A thermally-aware performance analysis of vertically integrated (3-D) processor-memory hierarchy

Three-dimensional (3D) integrated circuits have emerged as promising candidates to overcome the interconnect bottlenecks of nanometer scale designs. While they offer several other advantages, it is expected that the benefits from this technology can potentially be off-set by thermal considerations which impact chip performance and reliability. The work presented in this paper is the first attempt to study the performance benefits of 3D technology under the influence of such thermal constraints. Using a processor-cache-memory system and carefully chosen applications encompassing different memory behaviors, the performance of 3D architecture is compared with a conventional planar (2D) design. It is found that the substantial increase in memory bus frequency and bus width contribute to a significant reduction in execution time with a 3D design. It is also found that increasing the clock frequency translates into larger gains in system performance with 3D designs than for planar 2D designs in memory intensive applications. The thermal profile of the vertically stacked chip is generated taking into account the highly temperature sensitive leakage power dissipation. The maximum allowed operating frequency imposed by temperature constraint is shown to be lower for 3D than for 2D designs. In spite of these constraints, it is shown that the 3D system registers large performance improvement for memory intensive applications.