Designing a new microprocessor is extremely time-consuming. One of the contributing reasons is that computer designers rely heavily on detailed architectural simulations, which are very time-consuming. Recent work has focused on statistical simulation to address this issue. The basic idea of statistical simulation is to measure characteristics during program execution, generate a synthetic trace with those characteristics and then simulate the synthetic trace. The statistically generated synthetic trace is orders of magnitude smaller than the original program sequence and hence results in significantly faster simulation. This paper makes the following contributions to the statistical simulation methodology. First, we propose the use of a statistical flow graph to characterize the control flow of a program execution. Second, we model delayed update of branch predictors while profiling program execution characteristics. Experimental results show that statistical simulation using this improved control flow modeling attains significantly better accuracy than the previously proposed HLS system. We evaluate both the absolute and the relative accuracy of our approach for power/performance modeling of superscalar microarchitectures. The results show that our statistical simulation framework can be used to efficiently explore processor design spaces.

In multimedia processing, it is well-known that the sum-of-absolute-differences (SAD) operation is the most time-consuming operation when implemented in software running on programmable processor cores. This is mainly due to the sequential characteristic of such an implementation. In this paper, we investigate several hardware implementations of the SAD operation and map the most promising one in FPGA. Our investigation shows that an adder tree based approach yields the best results in terms of speed and area requirements and has been implemented as such by writing high-level VHDL code. The design was functionally verified by utilizing the MAX+plus II 10.1 Baseline software package from Altera Corp. and then synthesized by utilizing the LeonardoSpectrum software package from Exemplar Logic Inc. Preliminary results show that the design can be clocked at 380 MHz. This result translates into a faster than real-time full search in motion estimation for the main profile/main level of the MPEG-2 standard.