System-Level Design:Selecting Implementation and Packaging Styles for System Modules

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Selecting Implementation and Packaging Styles for System Modules

Packaging styles can range from single-chip dual-in-line packages (DIPs) to MCMs, boards, racks, and cases. Implementation styles include general-purpose processor, special-purpose programmable processor (e.g., signal processor), COTS modules, field programmable gate arrays (FPGAs), gate array, standard cell, and custom integrated circuits. System cost, performance, power, and design time constraints determine selection of implementation and packaging styles for many system designs. Tight performance constraints favor custom integrated circuits, packaged in MCMs. Tight cost constraints favor off-the-shelf processors and gate array implementations, with small substrates and inexpensive packaging. Tight power constraints favor custom circuits. Tight design time constraints favor COTS modules and FPGAs. If a single design property has high priority, the designer can select the appropriate implementation style and packaging technology. If, however, design time is crucial, but the system to be designed must process video signals in real time, then trade-offs in packaging and implementation style must be made. The optimality of system cost and power consumption might be sacrificed: the entire design might be built with FPGAs, with much parallel processing and at great cost and large size. Because time-to-market is so important, early market entry systems may sacrifice the optimality of many system parameters initially, and then improve them in the next version of the product.

Selection of implementation styles and packaging can be accomplished by adding some design parameters to the scheduling and allocation program, if that program is not already computationally intensive. The parameters added would include a variable indicating that a particular

• functional module was assigned a certain implementation style,

• storage module was assigned a certain implementation style,

• functional module was assigned a certain packaging style, and

• storage module was assigned a certain packaging style.

Some economy of processing could be obtained if certain implementation styles precluded certain packaging styles.

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