Underclocking
From Free net encyclopedia
Underclocking is the practice of modifying a microprocessor's speed settings to run at a lower clock speed than the manufacturer's specification. The purpose is generally to decrease heat dissipation and/or decrease electricity consumption. This can be done for the purposes of increasing system stability in high-heat environments, or to allow a system to run with a lower airflow (and therefore quieter) cooling fan or without one at all. However, this invariably comes at the expense of some system performance. There are several different underclocking competitions similar in format to overclocking competitions, except the goal is to have the slowest possible computer as opposed to the fastest. In essence underclocking is the opposite of overclocking.
Underclocking is very common in laptop computers and is beginning to emerge in desktop computers as well. On laptops the processor is usually underclocked automatically when the computer starts operating on batteries. In addition, several processors will underclock themselves when under a light processing load. This greatly increases battery life of laptop computers and can increase the processor's life span.
The Linux kernel, as well as other open-source kernels, include a feature known as CPU frequency modulation. This feature, often known as cpufreq, gives the system administrator a variable level of control over the CPU's clock speed. The kernel includes five governors by default: conservative, ondemand, performance, powersave, and userspace. The conservative and ondemand governors adjust the clock speed depending on the CPU load, but each with different algorithms. The performance, powersave, and userspace governors set the clock speed statically: performance to the highest available, powersave to the lowest available, and userspace to a frequency determined and controlled by the user.
The performance of underclocked machines can be surprisingly good when equipped with large amounts of RAM and a fast hard disk, rivalling normal or overclocked machines with little RAM and outdated hard disks.
See also
- Intel's SpeedStep
- AMD's Cool'n'Quiet