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Actual hardware fits into the dynamic analysis of designs in two ways: first as the computing engine on which the simulator of choice runs, and second as the goal of the design, verification, and construction process.
Several examples of hardware solutions to the computational burden imposed by simulators have been described [Denneau; Wang; Abramovici, Levendel, and Menon].
The Yorktown Simulation Engine [Denneau] is a special-purpose architecture designed to simulate up to two million gates at a rate exceeding three billion gate computations per second. The machine consists of 256 logic processors interconnected by a switch. Each has its own instruction and data memory and a functional unit capable of evaluating logic functions. In use, a gate-level simulation is divided into several networks of gates. Each network is loaded onto one logic processor. Internetwork communication is achieved through the interprocessor switch. In this way, parallel hardware is used to simulate the proposed design rapidly. There is a clear mapping between the intended hardware and the simulation.
Wang proposes a different solution: parallel hardware support for solving systems of nonlinear differential equations using the direct method [Wang]. This would provide rapid circuit-level simulation of designs larger than those that currently can be processed.
Other, intermediate solutions are also possible. For example, the simple addition of a floating-point coprocessor or a vector processor can speed the inner loops of the simulation calculations.
A side effect of a careful simulation effort is a set of test vectors that are used to debug the design. Those vectors can be used to test the prototype hardware, and simulation results can be compared to the results obtained from the real part.
The ultimate goal of the design, verification, and construction process is working hardware. The advent of multilevel simulation systems brings about the possibility of using hardware as part of the simulation of a large system. For example, if an ALU chip became available it might be used to replace the simulation of the ALU in the overall system. This would serve both as a testbed for the new hardware part and as a means of improving the performance of the simulation as a whole. Several commercial vendors market products that allow the intermixing of simulator and prototype hardware [VLSI].
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