Simulators play an important part in computer architecture research. As for specific microarchitecture study, which focuses on the accurate behavior of out-of-order scheduling, ALU contention, and function unit management, an over-simplified abstraction is not sufficient to represent modern processor organizations. Thus cycle-accurate simulators are introduced to describe the accurate behavior in target microarchitecture. In cycle-accurate simulators, the timing feature within function units is simulated. This paper presents PPSim, a cycle-accurate PowerPC instruction set simulator, which models the cache, branch prediction, and out of order pipeline in PowerPC microarchitecture.