Advanced Micro Devices in August will begin selling its quad-core "Barcelona" Opteron processors, models that answer Intel's current products but soon will face stiffer competition.

The first Barcelona models, formally called Quad-Core Opteron, will run at clock frequencies up to 2GHz and will be available in standard and low-power versions. Faster models, both of the standard and more power-hungry special-edition ilk, will arrive in the fourth quarter, the company said. The first servers using the chips will come in September.

"AMD has prioritized production of our low-power and standard-power products because our customers and ecosystem demand it, and we firmly believe that the introduction of our native Quad-Core AMD Opteron processor will deliver on the promise of the highest levels of performance-per-watt the industry has ever seen," Randy Allen, corporate vice president of AMD's server and workstation division, said in a statement.

AMD successfully carved a significant niche for itself in the server market with the release of the 64-bit Opteron processor family, gaining share against Intel's Xeon with better performance, lower power consumption and a faster transition to a dual-core design.

But Intel fought back in 2006. Its dual-core Xeon 5100 "Woodcrest" model fixed the performance problems midway through the year. Then, squeezing two of those silicon chips into a single electronics package gave Intel its Xeon 5300 "Clovertown" quad-core model toward the end of 2006.

AMD's Barcelona puts four cores on a single slice of silicon, an approach AMD calls "native quad-core," and the company has argued that Barcelona will outperform the Xeon 5300. The only problem: that comparison soon will become obsolete.

Intel's second-generation quad-core server processors, "Harpertown" a server member of Intel's "Penryn" family, will arrive this year, too, with the promise of better performance, lower power consumption and lower manufacturing costs by virtue of a manufacturing process with 45-nanometer features. AMD is only just now moving to a 65-nanometer process.

For decades, typical computer processors had a single processing engine, but dual-core models with two engines began arriving this decade as a way to try to improve performance without consuming inordinate amounts of power and producing corresponding amounts of waste heat. Now chipmakers have moved to quad-core and octo-core models; Sun Microsystems plans to debut its 16-core "Rock" chip in 2008.