The Power Saving Guide

Power Saving Fundamentals

Gone are the days when performance benchmarks were the only stats that mattered. When AMD and Intel CPU clock speeds first went above the Gigahertz mark * with speeds now approaching 4 GHz-* power consumption and heat dissipation caused processors to crash if not cooled properly. Although there were less power-hungry processor options available, Intel held the NetBurst course even with its dual-core devices, hiking up power consumption even more. However, the introduction of the Core 2 processor family turned the world upside down, as Core 2 delivers much more performance with power consumption that was almost cut in half. We believe that this is not enough, though, because the processor by far isn't the only one component with which you can save energy.

Resistance of electric circuits generates heat * whether we're talking about a processor with several hundred million transistors or an audio component with a fraction of the number of transistors. A powerful multimedia computer has at least four complex silicon products: The CPU, the graphics processor and two chipset components. If you add memory and voltage regulators, network and audio components, Firewire and additional storage controllers, you will count 30-70 individual chips, all of which consume energy and create heat. Scaling down transistor structures allows for the reduction of the operating voltage, which in turn reduces the electric resistance and lowers heat dissipation.

This has been the traditional approach to save power, but it has also been used to accelerate clock frequencies or to add even more transistors to support more features. Since higher transistor counts obviously increase heat dissipation as well, and since transistor numbers will continue to rise, AMD's and Intel's next-generation multi-core processors will not only be able to switch off unused transistors (sleep transistors) and functional units such as L2 cache segments, but we expect to see processors that will dynamically switch entire processing cores on and off to save energy. They will also probably accelerate a single processing core for single-threaded workloads (e.g. Intel EDAT * Enhanced Dynamic Acceleration Technology, which is expected for the Wolfdale and Yorkfield 45-nm processors). With most processors already supporting dynamic, workload-dependent clock speed adjustment, this clearly is the next logical step.

But what is happening in the other component areas of the PC? Doesn't a graphics card get much hotter than a processor? What is the power consumption of hard drives? Does memory require a lot of power? Do two versus four DIMMs make a noticeable difference in power consumption? Should I switch my display off when I go to lunch or will the system power management do the job? What if I switched off motherboard components that are not needed? We went to our test labs to find answers to these questions.

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