Leveraging CPU Electromagnetic Emanations for Voltage Noise Characterization

Worst-case dI/dt voltage noise is typically characterized post-silicon using direct voltage measurements through either on-package measurement points or on-chip dedicated circuitry. These approaches consume expensive pad resources or suffer from design-time and run-time overheads. This work proposes an alternative non-intrusive, zero-overhead approach for post-silicon dI/dt voltage noise generation based on sensing CPU electromagnetic emanations using an antenna and a spectrum analyzer. The approach is based on the observation that high amplitude electromagnetic emanations are correlated with high voltage noise. We leverage this observation to automatically generate voltage noise (dI/dt) stress tests with a genetic-algorithm that is driven by electromagnetic signal amplitude and to obtain the first-order resonance-frequency of the Power-Delivery LC-tank network. The generality of the approach is established by successfully applying it to three different CPUs: two ARM multi-core mobile CPU clusters hosted on a big.LITTLE configuration and an ×86-64 AMD desktop CPU. The efficacy of the proposed methodology is validated through VMIN and direct voltage noise measurements.