What you need to know about DSP chips. (digital signal processor) (Compute's Getting Started With: PC Sound)
by Richard O. Mann
The coming of DSP (Digital Signal Processor) chips is revolutionizing sound boards, modems, and voice-processing hardware. DSPs are powerful computer chips specially designed to deal with electronic representations of sound at unheard-of speeds. They multitask, they operate at lightning speeds, and they understand sound.
And they're priced so low that all but low-end sound boards are adopting them. Not only do DSPs provide high performance, but they can be reprogrammed through software-only upgrades. As new capabilities are developed, you add them to your sound card by running a program from a disk--no opening the computer case and prying off old chips to replace them, or replacing whole sound boards. It's a dream come true.
One board vendor spoke of having his basic sound board on the computer store shelf along with smaller boxes containing upgrades for advanced features such as QSound, reverb, sound alteration (which he called "psychoacoustic effects"), voice recognition, voice-to-text, video integration, telephony, and things we have yet to imagine.
DSP cards are also easy to install. There are no jumpers to change; you change the settings through software.
The primary DSPs being used in consumer-level sound boards are from Sierra Semiconductors (called the Aria chip set), Analog Devices, IBM (the Mwave chip), and Creative Labs (the ASP chip). Boards equipped with these DSPs (and others) offer enough interfaces and emulations to satisfy most standard needs.
When you get into more advanced functions, however, developers have to write their software directly for the particular chip set involved. Interplay's Star Trek game with voice recognition, for example, only works with the boards using the Aria Listener chip. Advanced audio functions have no standard interfaces yet, so be aware that at least for a while, the fancier DSP functions require software written specifically for your card.
DSPs as Add-Ons
Several sound board makers sell basic sound cards without DSPs but offer DSP upgrades on daughterboards or in other ways as add-ons. This can be an effective way to cycle into the DSP era.
While DSPs multitask, there are limitations as to what can happen simultaneously. Most boards are capable of two concurrent functions (such as wave-table music and FM-synthesis emulation for sound effects), but you'll need to make sure that any board you seriously consider can perform all the functions you want at the same time.
The Future of the DSP
DSPs offer a bright future for audio functions. There's
a lot of talk in the industry about moving the DSPs onto the motherboard to allow tighter integration with CPU functions. The future should hold additional audio wonders, including--we hope--more effective compression techniques to keep file sizes down.
The next sound card I buy will be DSP based, without question. Perhaps yours should be, too.