Clock frequency

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On basically all modern chips it is possible to reduce the clock frequency. Reducing the clock frequency makes the chip reduce its performance by having less cycles available per time unit. Reducing the clock directly saves energy because the power consumption goes down, but more importantly significantly less heat is produced. It allows for reduced fan speeds or sometimes even the removal of active cooling altogether.

On desktop machines, laptops or mobile platforms, the full computing power is hardly ever needed and the reduced performance should be no problem, if at all noticeable.

Changing the clock frequency is sometimes known as reclocking. Reducing the clock frequency is often known as underclocking or downclocking.

Contents

Advantages

  • Reduced heat generation.
  • Reduced electrical power consumption.
  • Longer hardware lifespan.
  • Increased stability.
  • Reduced noise from cooling parts due to reduced heat dissipation requirements.
  • Increased battery life.
  • Better compabillity with old applications.

Dynamic voltage scaling

A similar technique is dynamic voltage scaling. It is done to reduce power consumption and heat production. Reducing voltage by means of software is however only possible less often.

Implementations

In Windows systems the clock frequency can often be set manually in BIOS. With features like Intel's SpeedStep or AMD's Cool'n'Quiet this can done dynamically.

In the Linux kernel, a feature known as cpufreq, gives the system administrator a variable level of control over the CPU's clock rate.

Cases

Miserware is a company specialized in intelligent software power management. Their website has a lot of testimonials of satisfied customers. Their software called granola dynamically underclocks the microprocessor and, according to their own statement, saves up to 35% CPU energy and increases laptop battery life up to 20%.

In most smartphones and PDAs processors are underclocked by the manufacturer. This is done because an underclocked powerful processor has a better battery life than a fully clocked but slower processor.

Sources

This best practice was recognized as such by IT professionals, described in Energy efficient software.

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