Zesto: A cycle-level simulator for highly detailed microarchitecture exploration

For academic computer architecture research, a large number of publicly available simulators make use of relatively simple abstractions for the microarchitecture of the processor pipeline. For some types of studies, such as those for multi-core cache coherence designs, a simple pipeline model may suffice. For detailed microarchitecture research, such as those that are sensitive to the exact behavior of out-of-order scheduling, ALU and bypass network contention, and resource management (e.g., RS and ROB entries), an over-simplified model is not representative of modern processor organizations. We present a new timing simulator that models a modern x86 microarchitecture at a very low level, including out-of-order scheduling and execution that much more closely mirrors current implementations, a detailed cache/memory hierarchy, as well as many x86-specific microarchitecture features (e.g., simple vs. complex decoders, micro-op decomposition and fusion, microcode lookup overhead for long/complex x86 instructions).