Dual-chip architecture for mobile devices

As real-time, multimedia-rich applications such as videostreaming emerge in the next generation of smart phones and advanced mobile Internet appliances, the processing platforms that power them will need to be capable of processing more than ever before.

The processing demands placed on the engines and system architectures will escalate, as will the need to maintain or extend battery life so consumers can enjoy these new applications.

The challenge in the case of streaming video is the amount of bandwidth required to provide a real-time instantaneous datastream.

Streaming video also requires an engine capable of processing the videostream while performing other tasks. Designers of 2.5G and 3G platforms need to base their architectures on scalable and easily expandable concepts so new technologies and applications can be deployed quickly in response to changing market conditions.

A dual-processor architecture with a general-purpose or Reduced Instruction Set Computing processor and a digital signal processor (DSP) meets these needs better than a general-purpose processor.

As the computational and other capabilities of a wireless system increase to meet the requirements of streaming video applications, a partitioning of tasks between the two processors becomes more important. After all, who wants to watch a few minutes of video on a wireless device before it runs out of batteries? The system runs more efficiently when tasks are assigned to the processor best suited to the job.

For example, a DSP is better at processing the highly complex algorithms that make up the pictures and sounds of a music video clip, while a general-purpose processor is better at finding and retrieving a phone number. Divvying up these tasks to the processor best equipped to handle them will reduce power consumption and extend battery life. 2.5G and 3G wireless devices will have to provide expanded multimedia capabilities while keeping in line with the power expectations customers have come to expect from cell phones and PDAs.

As simple as dual-processor architecture may seem, it can pose challenges for wireless designers. Shared memory must be managed to avoid conflicts involving processors accessing the same memory location at the same time. Another challenge of dual-processor architecture is the difficulty that application developers may experience as their programs move across borders in the wireless architecture.

One solution is to create a high-level abstract layer - a bridge architecture - to which designers would develop applications. This would free them from having to delve into the details of the processors' operating characteristics and parameters.

With this bridge, a designer would develop programs in a high-level language for the architecture's general-purpose processor. When the DSP was needed to perform a task, the designer could call up the DSP through the high-level interface and application protocol interfaces present on the general-purpose processor. A programmer using this design could issue a command for streaming video and the bridge architecture would automatically assemble the resources needed for the task and relieve the designer of this responsibility.

If recent market trends are any indication, wireless communications technology will continue to advance at a rapid pace, but power consumption will always be a critical factor. Handheld, battery-powered systems can function only as long as their batteries last.

Batteries that can store more power would help, but a battery's capacity has physical limits. Ingenious wireless system designers can always reduce power consumption through architectural innovations and sound component selections.

De Gregorio is European wireless video development manager at Texas Instruments Inc.; Budagavi is a member of the technical staff at the digital signal processor research and development center at Texas Instruments; and Chaoui is worldwide OMAP software application and development manager at Texas Instruments. They can be reached at kbengtson@ti.com.

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