Power management

Of course, controlling power consumption at the chip level goes way beyond the transistor level, with clock speed reduction or even powering down whole blocks of the IC. However, the transistor-level leakage must be considered, either as a lower bound for reducing power consumption or in terms of how many new tricks must be implemented to keep it under control.

Providing opinion on who is better when it comes to something as complicated as a multicore microprocessor is a guessing game at best. Architecture and process technology are two major factors but are by no means the only considerations when selecting a server microprocessor. Upgrade path, power consumption and the interaction with chipsets and software could all come into play. Intel maintains a lead in process technology. AMD had a lead in architecture, but Intel's Nehalem will offer many of the innovations AMD introduced, along with a few of Intel's own. Whether you believe AMD or Intel is better at a given point in time, it's clear that competition is driving innovation, resulting in better products and more choice.

With a major architectural overhaul, Intel will be pushing server performance when versions of Nehalem come out next week, but AMD can maintain its "negawatt" lead with its power-saving transistor design. Incidentally, AISO, the hosting company that uses exclusively solar power, already uses servers built with AMD Opteron processors.

Acknowledgements

I want to thank Fayez Elchamaa for the transistor characterization data. To say probing 45-nm transistors is a challenge understates the effort, and Fayez had the benchmark data prepared in a very timely manner. Glenn He provided the floor-plan analysis.