Prompted by the development of new types of sophisticated field programmable devices (FPDs), the process of designing digital hardware has changed dramatically over the past few years. Unlike previous generations of technology, in which board level designs included large numbers of SSI chips containing basic gates, virtually every digital design produced today consists mostly of high-density devices. This applies not only to custom devices like processors and memory, but also for logic circuits such as state machine controllers, counters, registers, and decoders. When such circuits are destined for high volume systems they have been integrated into high-density gate arrays.
However, gate array NRE costs often are too expensive and gate arrays take too long to manufacture to be viable for prototyping or other low volume scenarios. For these reasons, most prototypes, and also many production designs are now built using FPDs. The most compelling advantages of FPDs are instant manufacturing turnaround, low startup costs, low financial risk and (since programming is done by the end user) ease of design changes.