Delivering thousands of amps to the next generation of high-speed digital designs is fast becoming the biggest design challenge for the next generation of custom multi-die packages, AI Chips, and cloud server applications. End-to-end power integrity digital twins with multiphase voltage regulators, PCB PDN with 100’s of capacitors, and dynamic loads are critical for mitigating expensive hardware failures when working with thousands of amps. This presentation will explore the model fidelity trade-offs and lessons learned from simulating the Picotest 2000 Amp Transient Load Stepper demo board with a 55-phase MPS horizontal power delivery topology and over 700 decoupling capacitors.