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This Issue's Topic: Redefining COTS signal processing

In a perfect world, a commercial off-the-shelf (COTS) signal processing board would have a single “magic” processor with infinite throughput and computational performance, zero latency and power consumption, and ease of programming in high-level languages. Since we are not living in a perfect world, however, and signal processing challenges are becoming more complex and widespread, designers have implemented a wide variety of COTS approaches that leverage existing real-world compute engines-all with varying compromises to the ideal solution.

By Jeff Milrod, BittWare President & CEO

General-purpose processors (GPPs), on the one hand, have tremendous performance along with well-established development tools and environments that make them relatively easy to program. On the other hand, however, these devices fall short where optimizing throughput, latency, or power are concerned.

Dedicated digital signal processors (DSPs) are superior to GPPs at optimizing for throughput, latency, and power, yet DSPs do not have as much raw computational performance or development tools necessitating multiprocessor solutions that are notoriously hard to develop on.

Recently, FPGAs have been brought to bear on the signal processing world as an adjunct, or even an alternative, to GPPs and DSPs. Clearly, FPGAs have tremendous advantages to standard processors since the throughput, computational performance, and latency can be optimally tuned in hardware, and recent generations, such as the Stratix III from Altera, have greatly improved power consumption. Even the traditional “Achilles heel” of using FPGAs for signal processing-the development environment and associated complexities-has been minimized via tremendous improvements in vendor and third-party tools.

There is one major drawback to the use of FPGAs, however, that the argument above neglects to discuss. While an FPGA can perform impressive processing, it is not a processor, and therefore does not have an internal architecture, instruction set, data paths, or a peripheral set. In fact, an FPGA simply provides the raw materials and components that enable-and require-a user to create everything from scratch. While the open-ended potential is understandably attractive to the engineer trying to find creative solutions to difficult signal-processing problems, this “dirty little secret” of FPGAs often unwittingly undermines the whole purpose of COTS.

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