AMD has pumped up the performance of its Athlon 64 X2 dual-core processor and cooled down two single-core Athlon 64 processors.

The top-of-the-range AMD Athlon 64 X2 dual-core processor is now the 6000+, with a clock speed of 3GHz and 2 MB of L2 cache. It sells for $464 in quantities of 1,000 or more. The previous fastest model, the 5600+ with a clock speed of 2.8GHz, now sells for $326 in quantities of 1,000 or more.

With its high-performance dual-core systems, AMD hopes to profit from the introduction of Microsoft's Vista, which places greater demands on computing hardware.

There's no speed boost for the single-core Athlon 64 processor, but AMD is now manufacturing the 3500+ and 3800+ models using a 65-nanometer production process, reducing the chips' die-size and energy consumption while offering the same computing performance.

The latest versions consume 45 watts, compared to 62 watts for the previous generation, in which the smallest features etched on the chips had a spacing of 90nm. The 3500+ sells for $88 in quantities of 1,000 or more, and the 3800+ for $93.

The faster dual-core chips will appeal primarily to gaming enthusiasts, and will appear shortly in PCs from Alienware and Voodoo, the gaming PC divisions of Dell and HP respectively, said AMD.

Fujitsu Siemens will use the lower-power processors in its Esprimo enterprise desktop range, which it promotes as an energy-efficient range, the company said.

Two weeks ago, AMD introduced new dual-core Opteron processors for servers that are either faster or consume less power than previous chips.

While AMD had begun to pull ahead in the market for low-power server and desktop chips, Intel is fighting back.

Last month, Intel persuaded Sun Microsystems Inc. to use its Xeon processors in future servers and workstations based on the x86 architecture. Sun had only used AMD chips in those machines in recent years, and will now use chips from both manufacturers.

At the top of the scale, Intel took the lead in the market for quad-core server chips last November, with the launch of its Xeon 5300 series, previously known as Clovertown. AMD won't introduce its range of energy-efficient quad-core server processors, code-named Barcelona, until the middle of this year.