Besides making the interconnects between transistors shorter, chipmakers are working to make them smoother. Over the last few years, for instance, one material that's been migrating into CPUs has been copper, which boosts performance because -- as every home electrician knows -- it's an excellent electrical conductor.

Using copper in CPUs would seem to be a no-brainer. But before 1997, lower-conductivity aluminum was used instead, because copper atoms could leak into or "poison" the transistors. IBM pioneered a way to stop that from happening, followed in 1998 by a venture between AMD and Motorola that led to the first copper-interconnect desktop PC processors.

Most chips today take advantage of copper, with vendors busily searching for an even more efficient successor. One innovation, explains Glaskowsky, is to place an insulator between the silicon and transistor layers of the chip, in a process called silicon-on-insulator (SOI): "Separating the transistors from the silicon base allows them to move faster, because they're not being dragged down by having the silicon nearby."

What drags them down is a buildup of electrical charge called parasitic capacitance; according to AMD, SOI design can cut this drag by 20 to 25 percent -- or, alternatively, slice a CPU's power consumption in half without slowing performance.

While SOI technology is available today in the PowerPC processors of high-end Apple Macs, "it will be adopted more slowly by the x86 companies because they need to manufacture chips in higher volumes," Glaskowsky says. AMD has promised to take the plunge, incorporating SOI in its Hammer family of CPUs due in the first half of 2003.

Rival Intel says it's chosen a different technique to tweak a processor's performance -- strained silicon, which changes the silicon lattice structure to speed the flow of electrons through it, like stretching a piece of fishnet fabric to make the holes bigger. Intel says the strained-silicon design that will debut with its 90-nanometer "Prescott" CPUs enhances drive current by 10 to 20 percent while adding only 2 percent to the manufacturing cost.

Chipmakers are also looking at the wires within chips in the quest to optimize performance. Intel's 90-nanometer designs will incorporate, and AMD's partner UMC is also pursuing, a mix of copper with "low-k dielectrics," a new kind of insulator between wires that increases signal speed and reduces power consumption. "The insulation around the wire influences how fast signals go through it," Glaskowsky explains. "By changing the insulation, you can make the wire carry signals faster."

The Incredible Shrinking Chip?

Some elements within a CPU are even smaller than its manufacturing process size -- Intel's current, 0.13-micron Pentium 4 includes transistors that measure just 60 nanometers, and the company says its 90-nanometer CPUs will feature 50-nanometer transistors whose gate oxides are literally only five atoms thick. Indeed, as processors get smaller and smaller, analysts predict they'll reach a point where they can't shrink any further -- at least not using silicon.

There's some debate as to when that point will be reached; some say this silicon Ragnarok is still 10 to 20 years away, while others warn it could occur as soon as five years from now. But there's no need to lie awake over this prospect, since researchers are busily mining areas that could if necessary yield replacements for silicon.

One potential alternative: carbon nanotubes, cylinders of carbon atoms as small as 10 atoms across -- 500 times smaller than today's silicon-based transistors. Though far from optimized, nanotube transistors that outperform the silicon originals have already been created in the lab, says Phaedon Avouris, manager of nanoscale science and technology for IBM in Yorktown Heights, N.Y.

The first appearance of nanotubes in commercial products is expected next year, with several companies promising flat-panel displays based on the technology. Such screens are touted to have long lifetimes (over 10,000 hours), with wider viewing angles, lower viewing angles, and ultimately less cost than today's LCDs.