Underclocking
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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 or decrease electricity consumption. This is usually 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. In essence underclocking is the opposite of overclocking. For example a Pentium 4 Processor clocked at 2.4GHz can be underclocked to 1.8GHz and run lower fan speeds.
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[edit] When used
Automatic underclocking is very common on laptop computers and is beginning to emerge on desktop computers as well. In laptops the processor is usually underclocked automatically whenever the computer is operating on batteries. Most newer notebook and some desktop processors (see Cool'n'Quiet) will underclock themselves automatically when under a light processing load.
In addition, other components can also be underclocked such as the videocard or RAM.
There are also several different underclocking competitions similar in format to overclocking competitions, except the goal is to have the lowest clocked computer as opposed to the highest.
[edit] Advantages
- Longer hardware lifespan.
- Lower heat dissipation.
- Lower electrical consumption.
- Higher stability.
- Faster Access to Ram. ( Due to lower multiplier thus the CPU will not waste clock cycles.)
[edit] Disadvantages
- Lower performance.
[edit] In practice
[edit] Linux
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. Unlike the ondemand governor, the conservative governor doesn't jump to maximum frequency on CPU load and decreases the frequency step by step on CPU idle, but 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 speed statically: performance to the highest available, powersave to the lowest available, and userspace to a frequency determined and controlled by the user.
[edit] Windows
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.
[edit] Performance
The performance of underclocked machines can be surprisingly good when equipped with large amounts of RAM and a fast hard disk, rivaling normal or overclocked machines with little RAM and outdated hard disks.
[edit] See also
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CPU power saving technologies
(italics indicate technologies for non-x86 processors) |
[edit] External links
- Newsforge article: "Underclocking: what's the rush?"
- CPU Undervolting & Underclocking A Primer From SilentPCReview.com
- Underclocking a gameboy classic tutorial
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