Architectural differences of efficient sequential and parallel computers

In this paper we try to conclude what kind of a computer architecture is efficient for executing sequential problems, and what kind of an architecture is efficient for executing parallel problems from the processor architect's point of view. For that purpose we analytically evaluate the performance of eight general purpose processor architectures representing widely both commercial and scientific processor designs in both single processor and multiprocessor setups. The results are interesting. The most efficient architecture for sequential problems is a two-level pipelined VLIW architecture with few parallel functional units. The most efficient architecture for parallel problems is a deeply inter-thread superpipelined architecture in which functional units are chained. Thus, designing a computer for efficient sequential computation leads to a very different architecture than designing one for efficient parallel computation and there exists no single optimal architecture for general purpose computation.