DIVA: a reliable substrate for deep submicron microarchitecture design

Building a high-performance microprocessor presents many reliability challenges. Designers must verify the correctness of large complex systems and construct implementations that work reliably in varied (and occasionally adverse) operating conditions. To further complicate this task, deep submicron fabrication technologies present new reliability challenges in the form of degraded signal quality and logic failures caused by natural radiation interference. In this paper, we introduce dynamic verification, a novel microarchitectural technique that can significantly reduce the burden of correctness in microprocessor designs. The approach works by augmenting the commit phase of the processor pipeline with a functional checker unit. The functional checker verifies the correctness of the core processor's computation, only permitting correct results to commit. Overall design cost can be dramatically reduced because designers need only verify the correctness of the checker unit. We detail the DIVA checker architecture, a design optimized for simplicity and low cost. Using detailed timing simulation, we show that even resource-frugal DIVA checkers have little impact on core processor performance. To make the case for reduced verification costs, we argue that the DIVA checker should lend itself to functional and electrical verification better than a complex core processor. Finally, future applications that leverage dynamic verification to increase processor performance and availability are suggested.