2.1. System-Design Goals

All system designers have three major tasks:

• achieve system-design goals

• minimize project costs

• reduce design risks

At the same time, rising system complexity conspires to make these tasks increasingly difficult. For example, a system designed in 1995 might have simple I/O requirements such as a few parallel and asynchronous serial ports. Today’s electronic systems bristle with USB, IEEE 1394, and Ethernet ports that employ many complex protocol layers. Consequently, system-processing requirements have grown and are growing dramatically. Increasingly, system designers turn to SOCs to achieve the system complexity and cost goals. However, due to its very nature, SOC design is inherently more costly and riskier than board-level design.

Because SOCs are physically smaller, run at lower power, and have greatly expanded abilities compared to board-level systems based on off-the-shelf ICs, system designers can tackle far more challenging designs that involve processing tasks such as complex data encoding and decoding (for audio and video compression), encryption, and signal processing. The greatly increased systems complexity incurred by these additional processing loads increases design risk—complicated systems are harder to design and debug. SOCs are inherently riskier and more costly to develop than board-level designs because respinning a circuit board takes a day or a week. Respinning a chip takes months.