AMD has made its Opteron server processors cooler by a quarter. The company has reduced the maximum thermal output of its 90-nanometer chips by 25 percent compared to the previous generation.

The 90nm version of the Opteron and Athlon 64 processors will consume 67 Watts of power under maximum operating conditions, AMD said during a presentation to financial analysts. The 130nm Opterons consume an equivalent 89 Watts.

AMD released the 90nm Athlon 64 desktop processors with little fanfare earlier this year, and chose to implement the same strategy for the 90nm Opteron chips. An AMD spokeswoman confirmed that four new 90nm Opteron chips began shipping earlier this week, but the company did not issue a press release to mark the occasion.

Power consumption has become almost as important as performance, as chip makers have run into problems with the transition to the 90nm process technology. Chip designers shrink the size of the features within the chip as well as the distance between individual wires on the chip in order to move to a new process technology. The size of the process technology denotes the distance between the beginning of a wire and the beginning of an adjacent wire.

Historically, chip makers have been able to reduce the amount of power consumed by a chip built on a new process technology because they can place more transistors on the newer chip. Those smaller transistors can run at slower clock speeds and still provide the same level of performance because there are more transistors working. There is a direct relationship between clock speeds and power consumption.

But the transition to the 90nm process generation has been marked by problems of current leakage. Transistor structures are now so small that current can pass through walls of transistors and leak out of the chip as heat. Intel's 90nm processors actually required more power than its 130nm chips, due in part to increased current leakage and the power-hungry design of Intel's Pentium 4 chips at high clock speeds.

AMD believes its silicon-on-insulator (SOI) technology was responsible for keeping power consumption and leakage in check during the 90nm transition, it said at an analyst conference in November. SOI is a process in which transistors are built on top of an insulating layer of silicon oxide.

AMD offers low-power versions of its 130nm Opteron processors, but has not confirmed whether it will continue to release lower power versions of 90nm chips. Starting next year, it does plan to include power management technology on Opteron processors that regulate the amount of power consumed by the chip depending on the workload of a particular application.

The company released new 90nm Opterons in each of its three categories. The Opteron 146 is designed for one-way servers and workstations, the Opteron 246 and 248 are designed for two-way servers, and the Opteron 846 is used in four-way servers. The x46 chips run at 2.0GHz, while the x48 chip runs at 2.2GHz.