An ARM926EJ-S™ microcontroller with a fully resonant clock distribution network and 16KB data and instruction caches has been implemented in 130nm bulk silicon. Workloads execute successfully across process and temperature corners, and at room temperature, typical-process chips run at clock speeds up to 200MHz with I.2V supply. At resonance, the microcontroller core dissipates 0.23mW/MHz, recovering 85% of the energy in its clock distribution network. Total power savings range from 20% to 35%, depending on application workload and computation profile.