Sep. 11--Those in the market for a new laptop this fall will find a batch of new, mid-priced models that promise less weight and longer battery life than traditional notebook computers, but more performance -- and a bigger screen and keyboard -- than they'd get with a netbook.

The new "ultrathin" models take advantage of low-voltage processor designs that draw less power and throw off less heat, which allows computer makers to put them in laptops that are under an inch thick and weigh less than five pounds. The low-voltage chips are variations on the processors used in traditional laptops, so they pack more computing power than the low-cost chips, such as Intel's Atom, that are found in most netbooks.

A few models were introduced earlier this year, including Hewlett-Packard's Pavilion dv2 and Acer's Timeline series. Dell has launched its own line, the Inspiron Z series, in recent weeks. Dozens of other ultrathin offerings from just about every computer maker are expected to hit retailers before the winter holidays.

Their sleek frames are intended to be reminiscent of premium laptops from Apple and other makers, although they may not offer all the features or souped-up performance. "It's not a MacBook Air," said PC analyst Mika Kitagawa of the Gartner research group, "but they're thin and nice looking.

At prices between $500 and $800, the new laptops will cost several hundred dollars less than those premium models. And they will do

more than netbooks, which often sell for under $500 but have low processing speeds that are primarily suited for checking e-mail and surfing the Web.

Analysts say the notable success of netbooks, which generally have screens under 11 inches and keyboards that are smaller than standard, suggests there's also demand for an intermediate computer that blends attributes from both ends of the spectrum. The new ultrathins have screens ranging from 12 to 15 inches, with a standard-size keyboard.

The IDC research firm predicts netbook sales will more than double this year, from 11.6 million units in 2008 to 26.5 million in 2009. That's a big surge since their introduction in late 2007, but some consumers have been disappointed by their performance.

"When people try to do 3-D games on these netbooks or try to run their office applications, they tend to think it's a bit slow," Intel CEO Paul Otellini acknowledged in a conference call last month. Many netbooks are built with the Atom, a lower-power and lower-cost processor from Intel; they also have limited memory and other features.