Mitigating Inductive Noise in SMT Processors

Simultaneous Multi-Threading, although effective in increasing processor throughput, exacerbates the inductive noise problem such that more expensive electronic solutions are required even with the use of previously proposed microarchitectural approaches. We use detailed microarchitectural simulation together with the Pentium 4 power delivery model to demonstrate the impact of SMT on inductive noise, and to identify thread-specific microarchitectural reasons for high noise occurrences. We make the key observation that the presence of multiple threads actually provides an opportunity to mitigate the cyclical current fluctuations that cause noise, and propose the use of a prior performance enhancement technique to achieve this purpose.