The earth may be heating up, but Intel and Advanced Micro Devices are determined to keep PC warming trends in check.

A few years ago, fast single-core processors were causing fits in the PC industry, which tried to design systems to stay reliable as the temperature rose inside the PC chassis. Newer dual-core chips from both AMD and Intel run cooler than their single-core antecedents, much to the relief of PC designers.

But as both companies prepare products that use four processing cores, some wonder whether the current situation is just brief respite from the processor heat wave, especially as virtualization technologies reach the average user's system.

Intel, fresh off the launch of its Core 2 Duo chips, has announced plans to accelerate the introduction of a quad-core processor called Kentsfield, now expected in the fourth quarter. Not to be outdone, AMD later this year will release a product called "4x4," which is two AMD processors connected together on a high-end motherboard.

Both chipmakers' products will run hotter than the current processors, although it's unclear how much of a gap will exist. Intel hasn't released thermal specifications for Kentsfield yet, said Intel spokesman George Alfs. However, Kentsfield is essentially two Core 2 Duo processors bolted together onto a chip, so its thermal profile will certainly be higher than a single Core 2 Duo processor.

Likewise, 4x4 systems will consume more power than a dual-core AMD processor, said AMD's vice president of advanced marketing, Pat Moorhead. AMD plans to make the 4x4 product consume less power than two separate processors would in one system, although Moorhead declined to specify how the company plans to do that.

Taming the thermals
But Intel and AMD both say they've learned their lessons on power consumption and heat. A buildup of heat inside a PC can contribute to component failures, especially with sensitive items like hard drives, said In-Stat analyst Jim McGregor, during an interview at Intel's recent Core 2 Duo launch. That heat buildup requires noisy fans to keep the system cool, especially in notebooks.

Kentsfield and 4x4 are designed for high-end users who are willing to spend lots of money on a PC with cooling systems and powerful technology, said Dean McCarron, an analyst with Mercury Research. Mainstream users are not willing to take on that expense, he said.

When quad-core processors become the norm for the millions of PCs shipped each quarter, Intel and AMD will have to be vigilant about keeping power consumption at their current, PC-friendly levels. "When you push the thermals or the electric consumption too far outside the norm, that does put you into a niche segment," McCarron said.

Intel hasn't announced specific plans for quad-core processors beyond Kentsfield, Alfs said. Sources familiar with Intel's plans have indicated that when the company is ready to move from its current 65-nanometer manufacturing process to a 45-nanometer one next year, it will start with dual-core chips to make the transition easier. And then at some later date, it will be ready to build quad-core chips with the smaller 45-nanometer transistors on a single piece of silicon, unlike the multichip package used for Kentsfield. Chipmakers also usually see a decline in power consumption as they move to smaller transistors.

Alfs declined to comment on those plans, but did say that Intel plans to have a wide range of products available at various levels of power consumption. This could include low-power chips for smaller PCs or high-power chips for expensive gaming PCs. Intel will talk more about its plans for quad-core processors at the next Intel Developer Forum in September, Alfs said.

AMD's first quad-core processor, to be introduced in 2007 and made with its new 65-nanometer technology, will be released within the same thermal profile as its current dual-core chips, Moorhead said.

"Performance outside of an appropriate thermal envelope doesn't really do anybody any good," he said.

Envisioning virtualization
The definition of an appropriate thermal envelope could change, however, when virtualization technologies reach the desktop.

Virtualization software has been used primarily in servers to let IT managers run several different types of applications on a single server. Instead of running multiple servers at low utilization rates, managers can increase the utilization rate of a single server and reduce the number of boxes they have to nurture.

PC virtualization is some years away from becoming prevalent on the desktop, although early examples have started to appear in products such as Parallels, which allows Mac users to run Windows alongside the Mac operating system on Intel-based Macs.

Virtualization being still uncommon on PCs, most users currently hit the maximum performance of their processor only for short periods of time. But if they begin running numerous applications in multiple virtual environments on multicore processors, they'll be running their system at higher levels of performance for extended periods of time. That's when the inside temperature of PCs could once again start climbing.

Still, this is primarily a server problem at the moment, McCarron said. Heat could once again become an issue for PCs, however, when coupled with the demands for power from newer, more sophisticated graphics processors.

AMD's Moorhead said that although the PC industry isn't at that level yet, chipmakers will have to continue to build low-power transistors, improve the performance of power sensitive technology, and work with the PC industry to design efficient cooling products.

A dual-core or quad-core processor is still better for PC thermals than running two or four separate processors, McCarron said. But chip and PC companies will have to keep a close eye on the utilization rates of their multicore chips to stay cool into the next decade.