Supply boosting for high-performance processors in flip-chip packages

On-chip supply boosting can quickly restore a microprocessor core's power rail from near-threshold to super-threshold when critical code sections are encountered. We demonstrate a flip-chip implementation of a supply boosting technique, called Shortstop, which uses a transient supply rail and leverages the parasitic and intentional inductance of a package. To address package parasitic variation, an automatic tuning algorithm is shown. A 7.9mm2, 40nm CMOS prototype chip is attached to a custom ball grid array substrate, with integrated in-package inductors. Shortstop boosts a 2.7mm2 core from 0.5V to 0.75V in 14ns with only 27mV of droop on a shared 0.8V supply rail, marking a 57% faster transition with 67% lower supply noise than a dual-supply PMOS header design.