A few years ago, processor options were limited for systems with serious DSP requirements. One could select from a handful of off-the-shelf DSP processors, use inflexible application-specific chips or build a custom chip.

System designers today have the opposite problem: The myriad choices make selecting a processor tough. The diversity of applications complicates the choice.

In applications like cell phones, conventional DSPs set the standard for flexibility, energy efficiency and cost/performance. However, in other areas, innovative designs are boosting performance with VLIW and single-instruction, multiple-data techniques.

But many DSP applications don't require cutting-edge performance, and even lightweight general-purpose processors can do serious DSP work. By adding DSP-oriented features to their architectures, 32-bit embedded-processor vendors are addressing applications with higher DSP performance requirements. The increased DSP horsepower in these chips makes them competitive with DSPs in many applications.

Meanwhile, alternatives emerge. FPGA vendors are tackling DSP applications head on. FPGA vendors' investments in tools and intellectual-property building blocks let users translate many DSP algorithms into FPGA implementations.

Some of the most interesting approaches use novel combinations of established technologies. For example, some vendors unveiled customizable processor cores-processors whose data paths and instruction sets can be altered by a system-on-chip designer to enhance efficiency for a particular application. This approach is ideal for typical DSP applications that spend so much time in computation-intensive inner loops, and these loops often contain operations that don't map nicely to conventional processor instruction sets. By letting system designers add specialized instructions, customizable processors can sharply improve processor efficiency in many DSP applications.

This rapidly expanding array of processor technology for DSP can be overwhelming. Time-tested approaches seem temptingly safe. But system designers who carefully navigate the morass of options will find their time well-rewarded.

Jeff Bier is general manager of Berkeley Design Technology Inc., a DSP technology analysis and software development company.