The Yorktown Simulation Engine (YSE) is a high speed special purpose parallel processor designed and built at the I.B.M. Thomas J. Watson Research Center to simulate the logical operation of large digital networks. A full YSE configuration simulates networks of up to 2,000,000 gates at a rate exceeding 3 billion gate computations per second, doing more simulation in just eight hours than an IBM 370/168 does in an entire year. This paper reviews gate-level logic simulation and describes the architecture and hardware implementation of the YSE. A companion paper by G. Pfister and E. Kronstadt discusses the YSE software.