Resonant-Clock Design for a Power-Efficient, High-Volume x86-64 Microprocessor

AMD's 32-nm x86-64 core code-named “Piledriver” features a resonant global clock distribution to reduce clock distribution power while maintaining a low clock skew. To support a wide range of operating frequencies expected of the core, the global clock system operates in two modes: a resonant-clock (rclk) mode for energy-efficient operation over a desired frequency range and a conventional, direct-drive mode (cclk) to support low-frequency operation. This dual-mode feature was implemented with minimal area impact to achieve both reduced average power dissipation and improved power-constrained performance. In Piledriver, resonant clocking achieves a peak 25% global clock power reduction at 75°C, which translates to a 4.5% reduction in average application core power.