FPGAs crash the party

These days, digital signal processing enables everything from satellites to engine controllers. With their decades of experience, one would expect DSP processor vendors to have a lock on these applications. All they have to do is belly up to the all-you-can-eat buffet, right? Not if FPGA vendors can help it.

Until fairly recently, field-programmable gate arrays lacked the capacity to implement demanding DSP algorithms-and they were perceived as being too expensive and power-hungry to compete with DSPs anyway. One reason for these shortcomings was that FPGAs were slow to adopt new fabrication technologies. In recent years, however, FPGAs have vaulted forward to leading-edge processes. And, more recently, FPGA designers have added powerful DSP-oriented features, like hardwired multipliers, to their devices.

With these advances, FPGAs have turned the tables. BDTI recently completed a comparative study of FPGAs and DSPs for signal-processing applications. This study put the longstanding assumptions about FPGAs to the test with a new communications receiver benchmark. The results were stunning: A typical member of Altera's Stratix FPGA family can handle dozens of receiver channels, while high-end DSPs can't support even a single channel. And with prices for some FPGAs and DSPs in the same ballpark, FPGAs can wallop DSPs in terms of channels per dollar.

But there's no free lunch. Because they are so flexible, it can be hard to determine the best way to map an application into an FPGA. This is particularly problematic because most DSP application developers are accustomed to software design flows, not the hardware design flows of an FPGA. And the DSP-oriented development infrastructure for FPGAs pales in comparison to the infrastructure for established DSPs. These complications create a huge disadvantage. BDTI's analysis suggests that optimizing a complex DSP function can take more than five times as long on an FPGA as on a DSP.

Five years ago, FPGAs couldn't compete against DSPs, but today they are scooping up healthy servings of high-performance DSP application markets. Although FPGAs are still too expensive to compete in many applications, DSP vendors will have to shove harder to keep a hold of their piece of the high-performance pie.

Jeff Bier is general manager of Berkeley Design Technology Inc. (www.bdti.com), a dsp technology analysis and software development company. Kenton Williston of BDTI contributed to this column.