Cutting-edge high-performance systems demand larger and denser processors, but future lithographic nodes are expected to introduce higher manufacturing costs and yield challenges. Die-level integration technologies like passive interposer-based 2.5D have demonstrated the potential for cost reductions through die partitioning and yield improvement, but system performance and scalability may be impacted. Alternatively, active interposer technology, the intersection of 3D and 2.5D methodologies, can provide higher-performance interconnect networks to integrate chiplets, but the active interposer die is itself subject to cost and yield concerns. In this work, we perform a cost and performance comparison between traditional monolithic 2D SoCs, 2.5D passive interposers, and 2.5D/3D active interposers to demonstrate the trade-offs between the interposer types for current and future high-performance systems. This work introduces a multi-die core-binning cost model to demonstrate the yield improvements from interposer-based die partitioning of large multi-core processors. The relative cost and performance scaling trade-offs of passive and active interposer dies are then compared for the target systems, demonstrating that both methodologies can indeed provide cost-effective integration for different system requirements. Finally, this work demonstrates how the extra “prepaid” silicon area of the interposers can be leveraged for fault tolerance to improve yield and cost-effectiveness. In summary, this work concludes that both active and passive interposers can cost-effectively improve the functional and parametric yield of high-performance systems, together providing a cost versus performance space to meet a range of design requirements.

Negative bias temperature instability (NBTI) is an important lifetime reliability problem in microprocessors. SRAM-based structures within the processor are especially susceptible to NBTI since one of the pMOS devices in the memory cell always has an input of “0”. Previously proposed recovery techniques for SRAM cells aim to balance the degradation of the two pMOS devices by attempting to keep their inputs at a logic “0” exactly 50% of the time. However, one of the devices is always in the negative bias condition at any given time. In this paper, we propose a technique called Recovery Boosting that allows both pMOS devices in the memory cell to be put into the recovery mode by slightly modifying to the design of conventional SRAM cells. We evaluate the circuit-level design of a physical register file and an issue queue that use such cells through SPICE-level simulations. We then conduct an architecture-level evaluation of the performance and reliability of using area-neutral designs of these two structures. We show that Recovery Boosting provides significant improvement in the static noise margins of the register file and issue queue while having very little impact on power consumption and performance.

NBTI is one of the most important silicon reliability problems facing processor designers today. The impact of NBTI can be mitigated at both the circuit and microarchitecture levels. In this paper, we propose a multi-level optimization approach, combining techniques at the circuit and microarchitecture levels, for reducing the impact of NBTI on the functional units (FUs) of a high-performance processor core. We perform SPICE simulations to evaluate the impact of circuit-level design optimizations to reduce the NBTI guardband in terms of area, delay, and power. We then propose a set of NBTI-aware dynamic instruction scheduling policies at the microarchitecture level and quantify their impact on application performance and guardband reduction through execution-driven simulation. We show that carefully combining techniques at both these levels provides the most attractive solution to reducing the guardband while imposing the least overhead in terms of area, power, delay, and application performance.

Silicon reliability is a key challenge facing the microprocessor industry. Processors need to be designed such that they are resilient against both soft errors and lifetime reliability phenomena. However, techniques developed to address one class of reliability problems may impact other aspects of silicon reliability. In this paper, we show that redundant multi-threading (RMT), which provides soft error protection, exacerbates lifetime reliability. We then explore two different architectural approaches to tackle this problem, namely, dynamic voltage scaling (DVS) and partial RMT. We show that each approach has certain strengths and weaknesses with respect to performance, soft error coverage, and lifetime reliability. We then propose and evaluate a hybrid approach that combines DVS and partial RMT. We show that this approach provides better improvement in lifetime reliability than DVS or partial RMT alone, buys back a significant amount of performance that is lost due to DVS, and provides nearly complete soft error coverage.