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    Underclocking Experiments

    Underclocking Background Information

    Definition

    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 the need for heat dissipation devices or decrease the electrical power consumption.

    Basics

    See also ovreclocking

    Underclocking can provide increased system stability in high-heat environments, or can allow a system to run with a lower airflow (and therefore quieter) cooling fan or without one at all. For example, a Pentium 4 processor clocked at 2.4 GHz can be underclocked to 1.8 GHz and can then be safely run with reduced fan speeds. However, this invariably comes at the expense of some system performance.

    Underclocking is the opposite of overclocking.

    Newer and faster RAM may be "underclocked" to match older systems as an inexpensive way to replace rare or discontinued memory. This might also be necessary if stability problems are encountered at higher settings.

    In addition, other components can also be underclocked such as the videocard or RAM. This is primarily done when the components are experiencing stability problems running at their rated frequency specification.

    Some processors "underclock" automatically as a defensive measure, to prevent overheating which could cause permanent damage. When such a processor reaches a temperature level deemed too high for safe operation, the thermal control circuit activates, automatically decreasing the clock and CPU core voltage until the temperature has returned to a safe level. In a properly cooled environment, this mechanism should trigger rarely (if ever).

    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 rate. The kernel includes five governors by default: conservative, Ondemand, Performance, Powersave, and Userspace. The conservative and Ondemand governors adjust the clock rate depending on the CPU load, but each with different algorithms. The Ondemand governor jumps to maximum frequency on CPU load and decreases the frequency step by step on CPU idle, whereas the conservative governor increases the frequency step by step on CPU load and jumps to lowest frequency on CPU idle. The performance, Powersave and Userspace governors set the clock rate statically: performance to the highest available, Powersave to the lowest available, and Userspace to a frequency determined and controlled by the user.

    Underclocking can be done manually in the BIOS or with Windows applications, or dynamically using technologies such as Intel's SpeedStep or AMD's Cool'n'Quiet.

    The performance of an underclocked machine will often be better than might be expected. Under normal desktop use the full power of the CPU is rarely needed. Even when the system is busy a large amount of time is usually spent waiting for data from memory, disk, or other devices. Such devices communicate with the CPU through a bus which operates at a much lower speed. Generally speaking, the lower the speed of a CPU, the closer it's speed will be to that of the bus, and the less time it spends waiting.

    Advantages

    • Considerably longer hardware lifespan.
    • Reduced heat generation (and hence dissipation).
    • Reduced electrical power consumption.
    • Increased stability.
    • Reduced noise from mechanical cooling parts (i.e. removing fan)
    • Enables to closely monitor a process for its behavior at lower speed where a fast speed running of the process does not allow that.
    • It Enables programmer or technicians to run application that is running abnormally fast.

    Disadvantages

    • Slower speeds.
    Topics of Interest

    Undervolting (Dynamic voltage scaling) is a power management technique in computer architecture, where the voltage used in a component is increased or decreased, depending upon circumstances. Dynamic voltage scaling to increase voltage is known as overvolting; Dynamic voltage scaling to decrease voltage is known as undervolting. Undervolting is done in order to conserve power, particularly in laptops and other mobile devices, where energy comes from a battery and thus is limited. Overvolting is done in order to increase computer performance.

    Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License and Creative Commons Attribution-ShareAlike License.)

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