The characteristics of multimedia applications when executed on general-purpose processors are not well understood. Such knowledge is extremely important in guiding the development of multimedia applications and the design of future processors. In this paper, we characterize and optimize the performance of multimedia applications on superscalar processor exploiting data-level parallelism and thread-level parallelism with SIMD (Single Instruction Multiple Data) and SMT (Simultaneous MultiThreading) capacities. We show that SMT and SIMD superscalar processor is suitable for 3D geometry application and we characterize the execution in term of memory hierarchy, which is the main bottleneck. The results show that the latency is not fully recovered by SMT; the use of second-level data prefetching does not succeed in increasing the performance. With detailed analysis, we show that this problem comes from a pollution of the instruction window by the threads experiencing second-level cache misses, thus reducing the window available for the other threads. We thus propose a hardware mechanism (an architecture optimization) to predict second-level misses and control this pollution.