Over the past twenty years, processor designers have concentrated on superscalar and VLIW architectures that exploit the instruction-level parallelism (ILP) available in engineering applications for workstation systems. Recently, however, the focus in computing has shifted from engineering to multimedia applications and from workstations to embedded systems. In this new computing environment, the performance, energy consumption, and development cost of ILP processors renders them ineffective despite their theoretical generality.

This thesis focuses on the development of efficient architectures for embedded multimedia systems. We argue that it is possible to design processors that deliver high performance, have low energy consumption, and are simple to implement. The basis for the argument is the ability of vector architectures to exploit efficiently the data-level parallelism in multimedia applications. Furthermore, the increasing density of CMOS chips enables the design of cost-effective, on-chip, memory systems that can support the high bandwidth necessary for a vector processor.

To test our hypothesis, we present VIRAM, a vector architecture for multimedia processing. We demonstrate that the vector instructions in VIRAM can capture the data-level parallelism in multimedia tasks and lead to smaller code size than RISC, CISC, and VLIW architectures. We also describe two scalable microarchitectures for vector media-processors: VIRAM-1 and CODE. VIRAM-1 integrates a simple, yet highly parallel, vector processor with an embedded DRAM memory system in a prototype chip with 120 million transistors. CODE uses a composite and decoupled organization for the vector processor in order to simplify the vector register file design, tolerate high memory latency, and allow for precise exceptions support. Both microarchitectures provide up to 10 times higher performance than alternative approaches without using out-of-order or wide instruction issue techniques that exacerbate energy consumption and design complexity.




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