Effects of Building Blocks on the Performance of Super-Scalar Architectures

The inherent low level parallelism of Super-Scalar architectures plays an important role in the processing power provided by these machines: independent functional units promote opportunities for executing several machine operations simultaneously. From the view- point of the hardware designer it is very important to assess the influence of each functional unit, and the way they communicate, on the overall performance of the machine. Particularly, it is highly desirable to determine an upper bound in the number of additional functional units, which give significant performance improvement ratios. This work describes experiments that have been carried out to assess the effect of alternative instruction issue mechanisms, multiple functional units, instruction queues, common data bus and other hardware solutions on the performance of Super-Scalar machines. The assessment was obtained by interpreting non optimized object code of an actual processor on some basic machine models. The pa- per outlines the main aspects of the research, and shows that speed-up ratios of up to 3.35 times were observed during the interpretation of benchmark programs.