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11:20 PM

PDAs: Always Pushing The Barrier

Limitations to what PDAs can handle are a moving target, Giga VP Carl Zetie says. Check out the latest changes before ruling PDAs out of--or into--your platform plans.

In the PDA market, the only constant is change.

Today's PDAs are pretty amazing devices, especially compared with what they were just a few years ago. Consider the processor power of a Pocket PC 2002 running XScale at 400 MHz or more versus the earliest Windows CE devices, or compare the latest Palm with 16 Mbytes storage with its 512-Kbyte ancestor. Equally impressive are devices such as the Kyocera 7135 or the Sony Ericsson P800 that cram a full-fledged PDA into the form of a phone. Yet despite these advances, fundamental limitations in PDA and communicator technology still rule out some things we'd like to do. So how fast can we expect things to improve?

The technology that makes up a complete mobile or wireless package combines a complex stack of hardware, software, and infrastructure components. Each of those components has its own release cycle. PDAs push the limits of size, weight, and power, so these limits are often the barriers to further improvements. Some of the key cycle times are:

  • Minor software upgrades: Every six months to one year. These upgrades provide incremental improvements in capability, perhaps adding support for new markup languages in the built-in browser or adding hardware interfaces such as Secure Digital Memory support that enable new peripherals or greater storage.
  • Major software/operating-system upgrade: Every two to four years. These provide significant improvements, at least in theory. For example, Pocket PC 2002 added greatly improved security and mandatory upgradeable flash memory over previous versions, and Palm OS 5.0 will provide greatly enhanced multitasking. Upgrade cycles have accelerated recently and may come as fast as every 18 months in the future.
  • Memory (RAM) size: Doubling every year. Fundamental improvements in memory technology are on the same 18-month to two-year cycle as for PCs. However, the memory available in PDAs also is tied to cost, which has a cycle all its own that varies greatly in the short term. On average, the "typical" memory in PDAs has been more than doubling every year, with the maximum available memory growing slightly more slowly.
  • Processor speed: Incremental increases every three to six months or discontinuous jumps every two to four years (two different cycles affect processor speed). While a PDA stays within a single processor family, improvements come in comparatively small increments, and the rate of increase depends on whether faster processors are available for immediate adoption and whether faster versions can be added. For example, during the past three to four years, Palm OS PDAs have moved from 16-MHz Motorola DragonBall 68K CPUs through the 33-MHz processors found in most current devices to the 66-MHz processors found in the fastest devices. Meanwhile, Pocket PC-based devices have standardized on the StrongARM processor running at 206 MHz and no longer support MIPS or SH-3 RISC processors. More dramatic increases can occur when a PDA moves from one technology to another--for example, Palm's move from DragonBall 68K to ARM in the forthcoming Palm OS 5. Such discontinuous increases are typically tied to the major operating-system upgrade cycle. Note, however, that some devices may not exploit a processor's full speed to reduce power requirements and improve battery life. Also, without supporting changes in the operating system, a new processor alone may not provide the full performance boost, as has happened with the new 400-MHz XScale processors in the latest-generation Pocket PC devices. Consequently, these two cycles need to be considered together if you're going to achieve the maximum benefit.
  • Mass storage: The growth rate of technologies such as SmartMedia cards or Compact Flash Memory data-storage systems has roughly doubled every year. With microdrives from vendors such as IBM now offering 5 Gbytes or more of data in a Compact Flash format, and solid-state Compact Flash memory offering 1 Gbyte, availability of mass storage should very rarely be a limiting technology today. Toshiba even has a 10-Gbyte drive in PCMCIA format, expected to go to 20 Gbytes next year.
  • Network bandwidth: Tenfold increase every three to five years. Bandwidth on the cellular networks has almost the slowest and the most discontinuous change cycle. Data bandwidth is tied to the generational network upgrades of the wireless carriers, massive infrastructure changes that take place over three- to five-year periods. Under second-generation digital mobile networks, 14.4 Kbps was a normal maximum for mobile data, perhaps achieving 28.8 Kbps equivalent with software compression. Under the 2.5G networks being rolled out (CDMA 1xRTT and GSM/GPRS), expect 25 Kbps to 70 Kbps average performance without compression, increasing gradually to 80 Kbps, and potentially peaking at 150 Kbps. Future 3G networks promise users up to 2 Mbps when stationary, less when moving, but won't be widely available until 2005. Some intermediate relief may be offered by the growth of "hot spots," along with seamless LAN-to-WAN roaming, but such technologies are geographically very limited. Other experimental fixed-wireless technologies also may offer relief to urban road warriors.
  • Battery life: Fundamental power technology has changed very slowly compared with the PDA's other key technologies, although significant incremental improvements in size, weight, and life have been driven in recent years by demands of the cell-phone industry. Dramatic improvements in power technology are unpredictable, but near-term incremental improvements in battery life will come more predictably from better components, including more-efficient displays, CPUs with better power management as epitomized by the Transmeta Crusoe and Intel Xscale processors, and smarter software that can manage the system's power consumption according to need. Supplemental power sources are increasingly available--the number of mobile devices in use drives demand, including calls for user-swappable batteries, power sockets on airplanes, hand-wound and solar chargers, and other emergency fallbacks. We're also seeing a swing back from integrated batteries to user-swappable batteries.
  • The number of roles that a PDA can't fill grows smaller with every crank of these technology cycles. The physical limitations inherent in the device, such as the size of the keyboard and display, are likely to be the last to fall. Experimental technologies such as projected-light keyboards, fold-up screens, and robust voice recognition may defeat even those barriers. In the meantime, the modular computer offers a realistic way to compromise between size and power as needs change.

    Given these independent development cycles, it makes sense to re-evaluate the suitability of the PDA as a platform at least once a year. By identifying the fundamental limitations that make a project infeasible today and understanding that technology's cycle time, you can better understand the trade-off between compromising with today's technology and waiting for something better.

    Carl Zetie is VP of research at Giga Information Group.

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