Building Better Ultralight Computers

The Holy Grail of mobile computing is a portable device that has the power of a desktop computer, lasts more than a day on a single battery charge, and weighs next to nothing. Right now, such a computer is still a myth. But computer makers are pushing the limits of weight and power. Today's so-called ultralight computers, which retail from about $1,800 to more than $3,000, are less than an inch thick, weigh less than three pounds, and have the computing power of a typical year-old desktop. Yet many of the smallest, lightest computers are studded with tradeoffs. They, for example, won't last more than a few hours on a single battery, don't come with built-in CD or DVD drives, and have less powerful processors than "normal" PCs. "Right now, people do see that you have to compromise to get to the form factor," that is, the ideal size and weight, says Michael Abary, senior product marketing manager for Sony's Vaio line of notebook PCs. "But we're making plans to offset them [the compromises]."One of the most promising new technologies to help achieve that goal is a new breed of low-powered microprocessors that can vary the speeds at which they operate.During complex computing tasks - such as crunching a large amount of numerical data in a spreadsheet - the processors might run at their top rate, or "clock speed." But for less demanding tasks - running a word processor or playing music, for instance - the chip can slow way down.The chief advantage of these processors, including Intel's Mobile Pentium III-M and Transmeta Corp.'s Crusoe, is the power they save. At slow speeds, for example, they typically require less than 1 watt, which means a computer's rechargeable batteries will last much longer between charges. Meanwhile, labs are testing new battery technologies. For now, most rechargeable batteries, made of lithium, provide portable computers about four or five hours before they need to be recharged. But research into different, lighter materials - such as zinc combined with air - could produce batteries with greater "energy densities." If more power can be packed into less space, portable computers can be made even lighter than the current crop of ultralights. "Unfortunately, unlike a lot of electronic technology which sees a doubling in capabilities every 18 months, battery technology growth is only linear," says Tom Bernhard, director of product marketing for Fujitsu. By Bernhard's estimates, really interesting developments won't happen for another three to five years. While they wait for the battery improvements, computer makers are touting a new type of portable computer called the tablet PC, which they hope to offer for sale by next year. Compaq, NEC and Toshiba all showed off models at this week's Comdex computer trade show in Las Vegas. These computers - typically the size and shape of an 1.5-inch-thick stack of typing paper - feature a screen that users can "write" on using a plastic stylus. The software, a special version of Microsoft's new Windows XP operating system, can interpret those pen strokes. And, instead of using a computer mouse to click on icons, users will merely tap on the screen to access the Internet or start programs. Ted Clark, vice president for Compaq's Tablet PC, says such pen-based computers will have all the power, memory and features of an ordinary notebook computer.Such snazzy portables may not be as cheap as ordinary notebooks, however. Early tablet PCs were priced well above $3,000 because of expensive parts such as the touch-sensitive screen.