DSP, for many engineers in the field, is a proprietary device used to implement digital-signal processing functions. These conventional pieces of silicon have been used for years to quickly and
efficiently digitize analog signals, arithmetically alter that digital information in a desired way, then
convert the digital back into something sensory that we humans can typically see, hear, or feel.
These digital signal processors, or DSPs, are found throughout the world of electronic equipment,
from cell phones to flat-screen TVs.
Dedicated DSP processors and cores are still a widely popular means of achieving digital signal
processing needs. In little more than a few days time, a programmer can take a DSP chip and write
an algorithm that will efficiently perform the digital signal processing task required. But as CPUs
have incorporated arithmetic coprocessors and extensions that optimize digital signal processing
tasks, and as other silicon alternatives have emerged, the necessity of a separate DSP chip is no
longer viewed as inevitable. In fact, there seems to be increasing evidence that the negatives of
discrete DSP chips might outweigh their benefits.
First, there is the issue of fixed costs. All DSP chips are viewed as IP (intellectual property), and
as such, have per-use costs associated with them.While such considerations arenít much of an
impediment to a company producing a limited number of end products, many digital signal
processing needs occur in high-volume products where steep discounting of retail prices over a
short period of time requires the lowest per-unit cost possible.
Next, there is the issue of performance. Compared to either ASIC or FPGA hardware solutions,
a DSP chip is by far the slowest option. ASIC chips run as fast as the technology allows. Similarly,
an FPGA that has been optimized to perform a digital-signal-processing task, will run anywhere
from 10 times to more than 1000 times faster than a single DSP chip.Whereas a DSP processor
typically employs serial processing, the parallel capacities inherent to either ASIC or FPGA architecture
will always give them both a significant edge over DSPs.
Finally, the power drain of most DSP chips can quickly become an issue, especially if the end
product will rely on battery power to increase its portability. The explosion of battery-driven technologies
such as Wireless LANs brings this power issue to the forefront of engineering considerations.
While DSP chips are often quick to program into your system during the development phase,
their battery-hungry ways make them less attractive options for digital signal processing with
significant portability needs. Carter Horney, a WLAN researcher associated with Forward
Concepts, a DSP research company, puts it bluntly: "DSPs just draw too much power for portable
Access the entire document on the Mentor Graphics Corp. website.