Dual-core Xeons show thirst for power

Intel has caught up to rival Advanced Micro Devices with its dual-core chips for dual-processor and four-processor servers. But with the chips, Intel still lags AMD in one important domain: power consumption.

Intel recommends server maker design power and cooling around a chip's "thermal design power." TDP measures the power needed to run conventional software at full tilt and is generally about 90 percent of the maximum power that the chip could conceivably require.

Intel argues that its dual-core chips, code-named Paxville and released in October, can be dropped into the same server designs as their single-core predecessors. Indeed, Dell, IBM, Hewlett-Packard and others are doing just that. But from a power and cooling perspective, doing so isn't trivial.

The single-core "Irwindale" Xeon for dual-processor servers has a TDP of 110 watts and a maximum of 120 watts, according to Intel data sheets. But Paxville for dual-processor servers runs at 135 watts and 150 watts for the comparable figures.

In Xeon MP models for servers with four or more processors, the gap is significantly larger. The single-core "Cranford" has a TDP of 110 watts and a maximum power of 120 watts, but the dual-core Paxville Xeon figures increase to 165 and 173 watts, respectively.

In contrast, AMD's Opterons--single- and dual-core--consume a maximum of 95 watts, though the company sells faster 120-watt "special edition" models to Sun Microsystems. It also sells premium Opterons that use only 68 watts but that run at 2.2GHz, a step shy of the the current 2.4GHz top speed of mainstream Opteron models. Those premium models are used in IBM and HP blade servers, and a 2.4GHz version will go on sale to select customers in the first quarter of 2006, spokesman Phil Hughes said.

Intel isn't standing idly by. Like AMD, it offers slower models that consume less power. And in the second half of 2006, the chipmaker plans to bring its "next-generation microarchitecture"--a chip core derived from that used in the Pentium M chip for mobile PCs--to the server line.

Opteron's lower power consumption is an advantage that AMD and allies such as Sun have been quick to pounce on. For example, power issues got prominent placement in a Sun announcement Monday that NewEnergy Associates, an energy consulting company, bought Opteron-based Sun Fire X4200 servers to replace its older Intel systems.

"Power consumption and cooling costs were a big factor for us, and according to the projections we've run, replacing up to eight Intel processor-based servers with one Sun Fire X4200 server can save us between 60 to 79 percent in power watts of energy usage and can reduce heat output by 70 to 84 percent," said Neal Tisdale, NewEnergy's vice president of software development, in a statement.