Multilevel temporal-parallel event-driven simulation is a new radically different approach to simulation of designs described in Verilog HDL. It is based on a concept of time-parallel simulation applied to gate-level timing simulation. The simulation is performed in two steps: 1) fast reference simulation that runs on a higher, reference-level design model (typically RTL) and saves the design state at predetermined checkpoints; and 2) target simulation, which runs on a lower, gate-level model and distributes the simulation run slices to individual simulators. The paper addresses a number of important issues that make this approach practical: 1) finding initial state for each simulation slice; 2) resolving initial state mismatches; and 3) handling designs with multiple asynchronous clocks. Experimental results performed on industrial designs demonstrate the validity and efficiency of the method in terms of its performance and the debugging efficiency.

Simulation speedup offered by distributed parallel event-driven simulation is known to be seriously limited by the synchronization and communication overhead. These limiting factors are particularly severe in gate-level timing simulation. This paper describes a radically different approach to gate-level simulation based on a concept of temporal rather than conventional spatial parallelism. The proposed method partitions the entire simulation run into simulation slices in temporal domain and each slice is simulated separately. With each slice being independent from each other, an almost linear speedup is achievable with a large number of simulation nodes. This concept naturally enables “correct by simulation” methodology that explicitly maintains the consistency between the reference and the target specifications. Experimental results clearly show a significant simulation speed-up.

This paper describes a new and efficient solution to a distributed event-driven gate-level HDL simulation. It is based on a novel concept of spatial parallelism using accurate prediction of input and output signals of individual local modules in local simulations, derived from a model at a higher abstraction level (RTL). Using the predicted rather than actual signal values makes it possible to eliminate or greatly reduce the communication and synchronization overhead in a distributed event-driven simulation.

Simulation-based functional verification is characterized by two inherently conflicting targets: the signal visibility and simulation performance. Achieving a proper trade-off between these two targets is of paramount importance. Even though HDL simulators are the most widely used verification platform at the RTL and gate level, their major drawback is the low performance in verifying complex SOCs, especially when the high visibility over the design under verification is required. This paper presents a new, fast simulation method as an effective way to achieve both high simulation speed and full signal visibility. It is based on an original two-pass simulation approach. During the 1stpass, with the simulation running at full speed, a set of design states is saved periodically at predetermined checkpoints. During the 2ndpass, another simulation is performed, using any of saved checkpoints and providing 100% signal visibility for debugging. Our method differs from the traditional simulation snapshot approach in the amount and the way the design state is saved. Experimental results show significant speed-up compared to existing traditional simulation methods while maintaining 100% visibility.