VLSI architecture: past, present, and future

This paper examines the impact of VLSI technology on the evolution of computer architecture and projects the future of this evolution. We see that over the past 20 years, the increased density of VLSI chips was applied to close the gap between microprocessors and high-end CPUs. Today this gap is fully closed and adding devices to uniprocessors is well beyond the point of diminishing returns. To continue to convert the increasing density of VLSI to computer performance we see little alternative to building multicomputers. We sketch the architecture of a VLSI multicomputer constructed from c. 2009 processor-DRAM chips and outline some of the challenges involved in building such a system. We suggest that the software transition from sequential processors to such fine-grain multicomputers can be eased by using the multicomputer as the memory system of a conventional computer.