Definition
Overclocking is the process of running a computer component at a higher clock rate than it was designed for or was specified by the manufacturer, usually practiced by enthusiasts seeking an increase in the performance of their computers.
Basics
See also:
Some purchase low-end computer components which they then overclock to higher clock rates, or overclock high-end components to attain levels of performance beyond the specified values. Others overclock outdated components to keep pace with new system requirements, rather than purchasing new hardware.
People who overclock their components mainly focus their efforts on processors, video cards, motherboard chipsets, and random-access memory (RAM). It is done through manipulating the CPU multiplier and the motherboard's front side bus (FSB) clock rate until a maximum stable operating frequency is reached, although with the introduction of Intel's new X58 chipset and the Core i7 processor, the front side bus has been replaced with the QPI (Quick Path Interconnect); often this is called the Baseclock (BCLK). While the idea is simple, variation in the electrical and physical characteristics of computing systems complicates the process. CPU multipliers, bus dividers, voltages, thermal loads, cooling techniques and several other factors such as individual semiconductor clock and thermal tolerances can affect it. Every component has its unique limits with higher clocks and voltage. Two different CPUs may clock completely differently, one being stable with higher clocks at a similar temperature as the other. The bus and memory stability and tolerances also affect how stable an overclocking can be.
Considerations
There are several considerations when overclocking. First is to ensure that the component is supplied with adequate power to operate at the new clock rate. However, supplying the power with improper settings or applying excessive voltage can permanently damage a component. Since tight tolerances are required for overclocking, only more expensive motherboards—with advanced settings that computer enthusiasts are likely to use—have built-in overclocking capabilities. Motherboards with fewer settings, such as those found in Original Equipment Manufacturer (OEM) systems, do not support overclocking.
Cooling: High quality heatsinks are often made of copper.All electronic circuits produce heat generated by the movement of electrical current. As clock frequencies in digital circuits and voltage applied increase, the heat generated by components running at the higher performance levels also increases. This increased heat requires effective cooling to avoid damaging the hardware. In addition, some digital circuits slow down at high temperatures due to changes in metal–oxide–semiconductor field-effect transistor (MOSFET) device characteristics. Wire resistance also increases slightly at higher temperatures, contributing to decreased circuit performance. Because most stock cooling systems are designed for the amount of power produced during non-overclocked use, overclockers typically turn to more effective cooling solutions, such as powerful fans, larger heatsinks, heat pipes and water cooling. Size, shape, and material all influence the ability of a heatsink to dissipate heat. Efficient heatsinks are often made entirely of copper, which has high thermal conductivity, but is expensive. Aluminium is more widely used; it has poorer thermal conductivity, but is significantly cheaper than copper. Heat pipes are commonly used to improve conductivity. Many heatsinks combine two or more materials to achieve a balance between performance and cost.
Stability and functional correctness: As an overclocked component operates outside of the manufacturer's recommended operating conditions, it may function incorrectly, leading to system instability. Another risk is silent data corruption by undetected errors. Such failures might never be correctly diagnosed and may instead be incorrectly attributed to software bugs in applications or the operating system. Overclocked use may permanently damage components enough to cause them to misbehave (even under normal operating conditions) without becoming totally unusable.
Factors allowing overclocking: Overclockability arises in part due to the economics of the manufacturing processes of CPUs and other components. In most cases components with different rated clock rates are manufactured by the same process, and tested after manufacture to determine their actual ratings. The clock rate that the component is rated for is at or below the clock rate at which the CPU has passed the manufacturer's functionality tests when operating in worst-case conditions (for example, the highest allowed temperature and lowest allowed supply voltage). Manufacturers must also leave additional margin for reasons discussed below. Sometimes manufacturers produce more high-performing parts than they can sell, so some are marked as medium-performance chips to be sold for medium prices. Pentium architect Bob Colwell calls overclocking an "uncontrolled experiment in better-than-worst-case system operation".
Benchmarks are used to evaluate performance. The benchmarks can themselves become a kind of 'sport', in which users compete for the highest scores. As discussed above, stability and functional correctness may be compromised when overclocking, and meaningful benchmark results depend on correct execution of the benchmark. Because of this, benchmark scores may be qualified with stability and correctness notes (e.g. an overclocker may report a score, noting that the benchmark only runs to completion 1 in 5 times, or that signs of incorrect execution such as display corruption are visible while running the benchmark).
Manufacturer and vendor overclocking: Commercial system builders or component resellers sometimes overclock to sell items at higher profit margins. The retailer makes more money by buying lower-value components, overclocking them, and selling them at prices appropriate to a non-overclocked system at the new clock rate. In some cases an overclocked component is functionally identical to a non-overclocked one of the new clock rate, however, if an overclocked system is marketed as a non-overclocked system (it is generally assumed that unless a system is specifically marked as overclocked, it is not overclocked), it is considered fraudulent.
Advantages:
- The user can, in many cases, purchase a lower performance, cheaper component and overclock it to the clock rate of a more expensive component.
- Higher performance in games, encoding, video editing applications, and system tasks at no additional expense, but at an increased cost for electrical power consumption. Particularly for enthusiasts who regularly upgrade their hardware, overclocking can increase the time before an upgrade is needed.
- Some systems have "bottlenecks," where small overclocking of a component can help realize the full potential of another component to a greater percentage than the limiting hardware is overclocked. For instance, many motherboards with AMD Athlon 64 processors limit the clock rate of four units of RAM to 333 MHz. However, the memory performance is computed by dividing the processor clock rate (which is a base number times a CPU multiplier, for instance 1.8 GHz is most likely 9x200 MHz) by a fixed integer such that, at a stock clock rate, the RAM would run at a clock rate near 333 MHz. Manipulating elements of how the processor clock rate is set (usually lowering the multiplier), one can often overclock the processor a small amount, around 100-200 MHz (less than 10%), and gain a RAM clock rate of 400 MHz (20% increase), releasing the full potential of the RAM.
- Overclocking can be an engaging hobby in itself and supports many dedicated online communities. The PCMark website is one such site that hosts a leader-board for the most powerful computers to be bench-marked using the program.
- A new overclocker with proper research and precaution or a guiding hand can gain useful knowledge and hands-on experience about their system and PC systems in general.
Disadvantages:
Many of the disadvantages of overclocking can be mitigated or reduced in severity by skilled overclockers. However, novice overclockers may make mistakes while overclocking which can introduce avoidable drawbacks and which are more likely to damage the overclocked components (as well as other components they might affect).
General
- The lifespan of a processor may be reduced by higher operating frequencies, increased voltages and heat, although processors rapidly become obsolete in performance due to technological progress.
- Increased clock rates and/or voltages result in higher power consumption.
- While overclocked systems may be tested for stability before use, stability problems may surface after prolonged usage due to new workloads or untested portions of the processor core. Aging effects previously discussed may also result in stability problems after a long period of time. Even when a computer appears to be working normally, problems may arise in the future. For example, Windows may appear to work with no problems, but when you re-install or upgrade Windows, you may receive error messages such as a “file copy error" during Windows Setup. Microsoft says this of errors in upgrading to Windows XP: "Your computer [may be] over-clocked. Because over-clocking is very memory-intensive, decoding errors may occur when you extract files from your Windows XP CD-ROM".
- High-performance fans used for extra cooling can be noisy. Older popular models of fans used by overclockers can produce 50 decibels or more. However, nowadays, manufacturers are overcoming this problem by designing fans with aerodynamically optimized blades for smoother airflow and minimal noise (around 20 decibels at approximately 1 metre). The noise is not always acceptable, and overclocked machines are often much noisier than stock machines. Noise can be reduced by utilizing strategically-placed larger fans, which are inherently less noisy than smaller fans; by using alternative cooling methods (such as liquid and phase-change cooling); by lining the chassis with foam insulation; and by installing a fan-controlling bus to adjust fan speed (and, as a result, noise) to suit the task at hand. Now that overclocking is of interest to a larger target audience, this is less of a concern as manufacturers have begun researching and producing high-performance fans that are no longer as loud as their predecessors. Similarly, mid- to high-end PC cases now implement larger fans (to provide better airflow with less noise) as well as being designed with cooling and airflow in mind.
- Even with adequate CPU cooling, the excess heat produced by an overclocked processing unit increases the ambient air temperature of the system case; consequently, other components may be affected. Also, more heat will be expelled from the PC's vents, raising the temperature of the room the PC is in - sometimes to uncomfortable levels.
- Overclocking has the potential to cause component failure ("heat death"). Warranties do not cover damage caused by overclocking. Some motherboards offer safety measures that will stop this from happening (eg. limitations on FSB increase) so that only voltage control alterations can cause such harm.
- Overclocking a PC component may void its warranty (depending on the conditions of sale).
- There is a risk of fire if devices are not properly cooled.
Incorrectly performed overclocking
- Increasing the operation frequency of a component will usually increase its thermal output in a linear fashion, while an increase in voltage usually causes heat to increase as the square of the voltage. Excessive voltages or improper cooling may cause chip temperatures to rise almost instantaneously, causing the chip to be damaged or destroyed.
- More common than hardware failure is functional incorrectness. Although the hardware is not permanently damaged, this is inconvenient and can lead to instability and data loss. In rare, extreme cases entire filesystem failure may occur, causing the loss of all data.
- With poor placement of fans, turbulence and vortices may be created in the computer case, resulting in reduced cooling effectiveness and increased noise. In addition, improper fan mounting may cause rattling or vibration.
- Improper installation of exotic cooling solutions like liquid or phase-change cooling may result in failure of the cooling system, which may result in water damage or damage to the processor due to the sudden loss of cooling.
- Sometimes products claim to be intended specifically for overclocking and may be just decoration. Novice buyers should be aware of the marketing hype surrounding some products. Examples include heat spreaders and heatsinks designed for chips which do not generate enough heat to benefit from these devices. (Memory chips, for example)
Limitations: The utility of overclocking is limited for a few reasons:
- Personal computers are mostly used for tasks which are not computationally demanding, or which are performance-limited by bottlenecks outside of the local machine. For example, web browsing does not require a high performance computer, and the limiting factor will almost certainly be the bandwidth of the Internet connection of either the user or the server. Overclocking a processor will also do little to help increase application loading times as the limiting factor is reading data off the hard drive. Other general office tasks such as word processing and sending email are more dependent on the efficiency of the user than on the performance of the hardware. In these situations any performance increases through overclocking are unlikely to be noticeable.
- It is generally accepted that, even for computationally-heavy tasks, clock rate increases of less than ten percent are difficult to discern. For example, when playing video games, it is difficult to discern an increase from 60 to 66 frames per second (FPS) without the aid of an on-screen frame counter. Overclocking of a processor will rarely improve gaming performance noticeably, as the frame rates achieved in most modern games are bound almost exclusively by the GPU at resolutions beyond 1024x768.
Overclocking graphics cards
Graphics cards can also be overclocked, with utilities such as NVIDIA's Coolbits, or the PEG Link Mode on ASUS motherboards. Overclocking a video card usually shows a much better result in gaming than overclocking a processor or memory. Just like overclocking a processor, sufficient cooling is a must. Many graphics cards overheat and burn out when overclocked too much.
Sometimes, it is possible to see that a graphics card is pushed beyond its limits before any permanent damage is done by observing on-screen distortions known as artifacts. Two such discriminated "warning bells" are widely understood: green-flashing, random triangles appearing on the screen usually correspond to overheating problems on the GPU (Graphics Processing Unit) itself, while white, flashing dots appearing randomly (usually in groups) on the screen often mean that the card's RAM (memory) is overheating. It is common to run into one of those problems when overclocking graphics cards. Showing both symptoms at the same time usually means that the card is severely pushed beyond its heat/speed/voltage limits. If seen at normal speed, voltage and temperature, they may indicate faults with the card itself.
Some overclockers use a hardware voltage modification where a potentiometer is applied to the video card to manually adjust the voltage. This results in much greater flexibility, as overclocking software for graphics cards is rarely able to freely adjust the voltage. Voltage mods are very risky and may result in a dead video card, especially if the voltage modification ("voltmod") is applied by an inexperienced individual. It is also worth mentioning that adding physical elements to the video card immediately voids the warranty (even if the component has been designed and manufactured with overclocking in mind, and has the appropriate section in its warranty).
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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