Intel's overarching goal is to promote the idea of an "applications processor" that works independent of baseband functions, which will overload processors with heavy signal processing functions once 384-kilobit/second wireless bit rates become the norm.

Intel has proposed a new set of APIs intended to simplify the separation of application processing functions from baseband functions, and to give software developers hooks into the XScale microarchitecture.

"The applications and client should be developed separately from the communications stack. We want to free them so that they can develop at their own pace," according to Ronald Smith, vice president and general manager of Intel's wireless communications and computing group, speaking at the recent Intel Developer Conference here.

Under Intel's plan, developers of PDAs or cell phones will plant one or two XScale processors in their designs, depending on the platform's requirements. In low-end cellular handsets, for example, one CPU would handle Layer 2 and 3 protocol stacks as well as operating system control functions. As with today's designs, this CPU would handle baseband functions, and could be scaled for both performance and power consumption.

To demonstrate XScale's processing capability, Intel showed a system based on an early tapeout of a 0.18-micron processor that integrated a processor core, cache memory, PLL and MAC, but not the I/O. The company pushed the device to run at 1 GHz while consuming 1.55 Watts, and then brought it down to 50 MHz, at which point power dissipation fell to 10 milliwatts.

At 200 MHz, the device could process 254 million instructions per second, or enough to handle streaming video in a handheld terminal, said Jay Heeb, engineering director for the XScale microarchitecture. But even with that level of scalability, the processor will have little horsepower remaining for new applications running on 3G wireless systems, said Patrick Reilly, director of Intel's wireless computing enhancement architecture lab.

The separation of application and baseband functions has also drawn interest in Japan, where 3G services are set to launch next spring. Mitsubishi Electric Corp. and NEC Corp. both plan to use Intel's current StrongARM processor in 3G phones, and NEC's chip division is developing its own application processor for next-generation handsets, said Keiichi Shimakura, deputy president of NEC's electron device division.

Intel's first XScale processors are set to be announced by year's end, though Intel officials have offered scant details. Smith said he expects the first wireless systems using XScale processors to appear in products by the second half of 2001.

On the software side, Intel is developing a set of application programming interfaces for user applications, operating systems and for "platform management," which includes testing and calibration. The APIs will be operating system independent, and will enable the top-down, object-oriented design of modular components, according to Intel.

While the APIs will be tuned for Intel's XScale processors, they can be used by any processor that supports the ARM instruction set, Smith said. Intel expects the interfaces to be defined by year's end, and plans to introduce a software development kit by the first half of next year.

Just as a standard instruction set and programming models gave rise to software development on the PC, Smith said he believes the same can be accomplished using common APIs and a general-purpose processor in mobile devices. Intel has already brought on board 10 application software companies that will use the APIs.

"When you write to a general-purpose processor, applications are scalable and you keep code compatibility," Smith said. "That has been extremely useful in the PC platform. Plus, there are a limited number of programmers in the world."

Separating applications processing from the communications stack should also eliminate some development delays, Intel said. Applications that are tied to the communications stack could lengthen the time it takes to obtain "Type" approval from government agencies every time a new application is added, Reilly said.