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PDA Processors, Part 1: ARM Wrestling February 5, 2003 Power to the Pocket With PC sales flatter than an interstate in Iowa, chip vendors are turning to handhelds for a hand up. Intel Corp. has supplemented its Pentium, Celeron, Xeon, and Itanium with a processor product line for PDAs and smart phones, dubbed XScale, to carry its dominance into this emerging market. AMD has stepped into the arena with last year's purchase of Alchemy Semiconductor. Of course, the established suppliers of handheld CPUs, Motorola and Texas Instruments, have no plans to cede the market to these invaders from the desktop space. The appeal for chip vendors is obvious: Even though PDA sales slipped last year, users who formerly owned a single, bulky PC are relying on a greater variety of digital devices, and expecting more from them. When you consider the growing appeal of organizer-enabled wireless phones (or is it cell-phone-enabled PDAs?), the stakes are high: Market researchers at IDC predict the global PDA market will grow around 50 percent annually through 2004. The technical challenges for handheld CPUs are obvious, too -- dwarfing, so to speak, even those of moving from the desktop to notebook environment. A typical laptop CPU draws just 25 or 30 watts of power, compared to recent desktop chips' 60 or 70 watts? Fine; cut that to less than one watt, and we'll talk. AMD boasts that the Athlon XP is a compact 80 square millimeters versus the Pentium 4's 146? One of Intel's cell-phone chips squeezes both a CPU and flash memory into a teensy 13 square millimeters. We'll address the handheld CPU market in two articles. This one will check out the chips that power today's handheld gadgets and see how they compare; next week, we'll discuss the new handheld processors and applications on the horizon. And right now, the big trend in handheld silicon is the migration to ARM-based designs. The Chipmaker Behind the Chipmakers ARM Ltd. is a U.K. company formerly known as Advanced RISC Machines, spun off from the British PC builder Acorn. Rather than selling silicon, ARM sells intellectual property -- partners like Intel and TI pay licensing fees for the right to build chips based on ARM's architecture. Typically, vendors customize their chips to tweak performance, but the core logic -- in, the company boasts, almost three-quarters of the 32-bit embedded RISC processors in the world -- is all ARM's. And while the company's designs have been used in mobile phones and Pocket PCs for years, it's never had the wide industry support it enjoys now. The ARM architecture offers vendors a compelling balance of processing power and low energy consumption. "Power [requirement] is generally the most significant aspect for handheld designs as it impacts directly on features perceived by the user, [such as] talk time and standby time," says David Cormie, product manager for CPU products at ARM. "Size is also very important, as it directly impacts manufacturing cost." Successive generations of the ARM architecture have walked a tightrope between adding performance and adding bulk or battery drain. For instance, while desktop and server fans are eager to move from 32- to 64-bit processing, ARM insists a complete 64-bit CPU would be too big and expensive for a PDA or smart phone. Its latest ARM11 architecture compromises by providing 64-bit data buses between the integer unit and the instruction and data caches, while its Thumb instruction set heads in the other direction by letting programmers mix 32- and short 16-bit instructions. The latter, ARM says, provide memory savings of up to 35 percent while still giving access to a full 32-bit address space. Other features of ARM11 -- introduced last October and not yet fully implemented by any of ARM's licensees -- range from special Java acceleration, designed to provide faster execution than a software-based Java virtual machine, to the ARMv6 instruction set's single-instruction-multiple-data (SIMD) multimedia extensions for up to quadruple performance with audio and video codecs (see CPU Planet's October 23, 2002 article on multimedia extensions -- Ed.) And while ARM11 and its eight-stage integer pipeline are expected to debut at 350MHz in 0.13-micron-process products, the company's roadmap leads to 1GHz at 0.10 microns. Though ARM-based chips are rapidly becoming dominant in the handheld market, no one silicon vendor can claim the same status. So far, PDA and CPU vendors have paired off in relatively neat teams, such as Garmin's choice of Motorola, Sony's of Intel, and Palm's of Texas Instruments. Let's look at some of today's variety of offerings, while sorting out chip names you may have heard, such as DragonBall, StrongARM, and XScale.