Editor’s Note: In the last month there has been a deluge of chips announced for wireless products. Many of these announcements came from industry leaders, and many of the announcements introduced significant new technologies. While we can’t cover all of the significant announcements from the last two months in this issue of the DSP Insider, we’ll highlight some of the most notable developments in the following feature article.
This February, Samsung, STMicroelectronics, and Texas Instruments announced new “application processors.” Application processors are intended for portable wireless products—particularly “smart” phones and wireless PDAs—running a powerful operating system like Pocket PC, Symbian, or Linux. These products have two types of computational loads. The first type of load is the “application” software, which includes the operating system and software like Web browsers and MP3 decoders. Wireless communications software constitutes the second type of load. As the name implies, an application processor is intended to run the operating system and application software, but not the communications software.
Like most existing application processors, the new processors—the Samsung S3C2410 SiP, the ST Nomadik, and the TI OMAP161x—are all based on the ARM architecture. These new processors are also alike in that they all use die stacking to place large memories inside the same package as the processor. Despite these basic similarities, these new processors are remarkably different. For example, the processors take widely differing architectural approaches to handling multimedia tasks. In addition to its ARM core, the ST Nomadik contains two “smart accelerators,” one for audio and one for video. Each accelerator consists of a ST MMDSP+ DSP processor core and audio- or video-specific hardware. In contrast to ST’s dual-accelerator approach, the TI OMAP161x supplements its ARM core with a single TI ’C55x DSP core. The Samsung S3C2410 SiP takes an even simpler approach: it contains no multimedia-specific features. Each of these approaches has tradeoffs. On one hand, specialized hardware tends to be more efficient than general-purpose hardware. On the other hand, specialized hardware tends to be harder to program and harder to adapt for unforeseen applications than general-purpose hardware.
As mentioned earlier, application processors target products with two types of computational loads: application software and communications software. One way to handle these loads is to use an application processor for the application software and a separate “baseband” processor for the communications software. This is the approach taken by ST, Samsung, and TI application processors discussed above. This approach is attractive for products with demanding application and communications loads such as high-end phones. The main drawback of this approach is that it is relatively expensive. For mid-range products with less demanding loads, it may be possible to use a single “integrated” processor that handles both the applications and the communications loads. Compared to the two-processor approach, the single-processor approach may offer less computational power, but it may also reduce chip counts—and hence system costs and size.
Last month Intel and Texas Instruments both announced integrated application/baseband processors. The TI OMAP73x contains three cores: an ARM core and a TI ’C54x DSP core for baseband processing, and a separate ARM core for application processing. Like the TI OMAP161x, the TI OMAP73x is available with “stacked” memory. In contrast to TI’s three-core approach, the Intel PXA800F contains only two cores: an XScale core (an Intel-specific derivative of the ARM architecture) and a Micro Signal Architecture core (a DSP core co-developed by Intel and Analog Devices). Baseband processing is split across the XScale core and the Micro Signal Architecture core; the XScale core also handles application processing. Like some versions the TI OMAP73x, the Intel PXA800F features large on-chip memories. However, the Intel PXA800F does not use stacked memory; the PXA800F processor cores and memories are combined on a single die.
While processors are key components of cell phones, PDAs, and other wireless products, these products are complex systems with numerous important hardware and software components. This complexity has two important implications. First, cell phone and PDA technologies are maturing, leaving fewer opportunities for innovation at the “nuts and bolts” level of design. As a result, many product designers prefer to focus development efforts on high-level features like eye-catching packages. Second, even where there are opportunities for technological innovations, the increasing complexities of cell phones and PDAs mean fewer companies can take advantage of these opportunities. As a result, “end-to-end” solutions that integrate the critical hardware and software components are much more attractive than stand-alone processors.
A number of companies announced end-to-end cellular handset solutions in the last month, including Analog Devices, Intel, and Texas Instruments. Of these announcements, the most significant may have been TI’s announcement of a 3G chipset, the TCS4105, which can be used with or without a TI OMAP161x application processor. No single feature of this chipset is particularly unusual. However, few other vendors can match TI’s portfolio of wireless-oriented components, which includes application processors, baseband processors, and analog components. As a result, there are few single-vendor offerings that are as complete and as integrated as the TI TCS4105.
The bevy of processors and chipsets announced in the last months is a mixed blessing for designers of wireless terminals. The good news is that there is a wealth of new choices available to system designers. The bad news is that choosing a solution will require careful evaluation of a large number of complex offerings.
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