In Part 3 of this article, we illustrate the performance results and scalability obtained by implementing the traditional explicit control-volume (CV)/finite-element (FE) and a recently developed and new, implicit, pure finite-element approach in symmetric multiprocessor machines as illustrated in the preceding Part 1 and Part 2. The results indicate that the current-generation symmetric multiprocessors (SMPs) with a medium to large number of processors can be effectively used as a supercomputer (Massively Parallel Platforms, MPPs) for large-scale complex geometries in scientific and engineering problems. The recently developed and new implicit pure FE methodology is shown to be physically accurate, computationally superior, and applicable to practical large-scale problems compared to the traditional explicit CV-FE on different SMP platforms (SGI Power Challenge and SGI Origin2000). For large-scale problems, the explicit CV-FE-based modeling/analysis becomes impossible to analyze within reasonable time or realistically impossible even with parallel processing for large-scale problems. In view of such considerations, as an illustration, a large, complex finite-element mesh of 809,505 elements and 405,327 nodes has been successfully analyzed using the implicit pure FE methodology and 40 processors within a reasonable time of 4.72 hours. The proposed parallel approaches have excellent parallel efficiency and optimal scalability when compared to other relevant results in computational sciences published in the literature, with the highest degree of portability of the software code to a wide range of parallel architectures.