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{{short description|Practice of increasing the clock rate of a computer to exceed that certified by the manufacturer}}
{{short description|Increasing processor speed beyond specification}}
{{Use American English|date=February 2023}}
{{Use American English|date=February 2023}}
{{Use mdy dates|date=February 2023}}
{{Use mdy dates|date=February 2023}}
{{Not to be confused with|odometer}}
[[Image:Overclock.jpg|thumb|upright=1.5|A computer [[BIOS]] on an ABIT NF7-S [[motherboard]] with an overclocked AMD [[Athlon&nbsp;XP]] CPU, running at 2,442 [[Megahertz|MHz]]<!-- Routine calculation: 148MHz x 16.5 = 2442MHz. -->]]
{{Original research|date=February 2023}}
In [[computing]], '''overclocking''' is the practice of increasing the [[clock rate]] of a [[semiconductor device]], such as a [[Processor (computing)|processor]], beyond its rated speed, potentially increasing its [[Computer performance#Processing speed|performance]].<ref>{{Cite web |title=What is Overclocking? Examining Pros and Cons |url=https://uk.crucial.com/articles/about-memory/what-is-overclocking |access-date=2025-08-09 |website=Crucial |language=en-gb}}</ref> Overclocked devices, however, may have shorter lifespans, become unstable and unreliable, and in extreme cases, be permanently damaged. Many manufacturers do not cover damage from overclocking in their [[Warranty#Sale of goods|warranties]], while some allow it inside a predefined safety margin.
[[Image:Overclock.jpg|thumb|upright=1.5|Overclocking [[BIOS]] setup on an ABIT NF7-S [[motherboard]] with an AMD [[Athlon&nbsp;XP]] processor. [[Front side bus]] (FSB) frequency (external clock) has been increased from 133&nbsp;[[Hertz|MHz]] to 148&nbsp;MHz, and the CPU [[clock multiplier]] factor has been changed from 13.5 to 16.5. This corresponds to an overclocking of the FSB by 11.3 percent and of the CPU by 36 percent.]]
In [[computing]], '''overclocking''' is the practice of increasing the [[clock rate]] of a computer to exceed that certified by the manufacturer. Commonly, operating [[voltage]] is also increased to maintain a component's operational stability at accelerated speeds. [[Semiconductor device]]s operated at higher frequencies and voltages increase power consumption and heat.<ref>{{cite web|url=https://software.intel.com/en-us/blogs/2014/02/19/why-has-cpu-frequency-ceased-to-grow|author=Victoria Zhislina|date=2014-02-19|title=Why has CPU frequency ceased to grow?|publisher=Intel|access-date=2017-08-02|archive-date=2017-06-21|archive-url=https://web.archive.org/web/20170621074555/https://software.intel.com/en-us/blogs/2014/02/19/why-has-cpu-frequency-ceased-to-grow|url-status=live}}</ref> An overclocked device may be unreliable or fail completely if the additional heat load is not removed or power delivery components cannot meet increased power demands. Many device [[Warranty#Sale of goods|warranties]] state that overclocking or over-specification<ref>{{Cite web |title=LIMITED WARRANTY |url=https://www.intel.com/content/dam/support/us/en/documents/processors/Limited_Warranty_8.5x11_for_Web_English.pdf}}</ref> voids any warranty, but some manufacturers allow overclocking as long as it is done (relatively) safely.<ref>{{Cite web |title=Warranty Guide for Intel® Processors |url=https://www.intel.com/content/www/us/en/support/articles/000005494/processors.html#:~:text=Usage%20of%20overclocking%20and%20Intel,the%20processor%20and%20other%20components. |access-date=2025-03-22 |website=Intel |language=en}}</ref>


== Overview ==
== Overview ==


The purpose of overclocking is to increase the operating speed of a given component.<ref>5 Reasons to Overclock Your Next PC - Intel. (2024, August 16). Retrieved from <nowiki>https://www.intel.com/content/www/us/en/gaming/resources/5-reasons-to-overclock-your-next-pc.html</nowiki></ref> Normally, on modern systems, the target of overclocking is increasing the performance of a major chip or subsystem, such as the main processor or graphics controller, but other components, such as system memory ([[Random-access memory|RAM]]) or [[Bus (computing)|system buses]] (generally on the [[motherboard]]), are commonly involved. The trade-offs are an increase in power consumption (heat), fan noise (cooling), and shortened lifespan for the targeted components. Most components are designed with a margin of safety to deal with operating conditions outside of a manufacturer's control; examples are ambient temperature and fluctuations in operating voltage. Overclocking techniques in general aim to trade this safety margin by setting the device to run in the higher end of the margin, with the understanding that temperature and voltage must be more strictly monitored and controlled by the user. Examples are that operating temperature would need to be more strictly controlled with increased cooling, as the part will be less tolerant of increased temperatures at higher speeds. Also base operating voltage may be increased to compensate for unexpected voltage drops and to strengthen signaling and timing signals, as low-voltage excursions are more likely to cause malfunctions at higher operating speeds.
A semiconductor device's processing speed depends on a variety of factors, including, but not limited to, its clock speed, [[microarchitecture]], the kind of [[software]] it's running, and the [[Memory bandwidth|bandwidth]], [[Memory latency|latency]] and size for [[Memory hierarchy|each level of]] its [[Computer memory|memory]]. All else being equal, a faster-clocked device can, though not necessarily, perform faster. <!-- This paragraph is worded somewhat conservatively to account for the fact that a chip's performance can be bottlenecked by other factors. If said bottleneck is extreme enough, the performance improvement from overclocking would reduce proportionally (until there's no performance improvement left).
 
The first sentence is written in this way to imply that a processor may not benefit from higher clocks if it's running crap software, have terribly small / slow memory, or that the software given to it is poorly suited / poorly optimized to the chip's microarchitecture; an example for the lattermost point is to run strictly serial branching codes (a sea of if-elses) on a GPU. -->Operating [[voltage]] is often increased to maintain a component's operational stability at accelerated speeds. Operating at higher frequencies and voltages increase power consumption and heat.<ref name=":0">{{Cite journal |last=Jang |first=Hyung Beom |last2=Lee |first2=Junhee |last3=Kong |first3=Joonho |last4=Suh |first4=Taeweon |last5=Chung |first5=Sung Woo |date=May 2014 |title=Leveraging Process Variation for Performance and Energy: In the Perspective of Overclocking |url=https://ieeexplore.ieee.org/abstract/document/6374616 |journal=IEEE Transactions on Computers |volume=63 |issue=5 |pages=1316–1322 |doi=10.1109/TC.2012.286 |issn=1557-9956 |quote=VF-overclocking [increases] power consumption [as it] is proportional to the clock frequency and the supply voltage squared. [Excessive] switching in transistors from [such overclocking also increases] the temperature of microprocessors [incurring] reliability loss.|url-access=subscription }}</ref> Overclocking a device introduces additional risks of failure, for example, by overheating when the increased heat load is not removed,<ref name=":0" /> or by the device requesting more power than its power supply can provide.{{cn|date=November 2025}}
While most modern devices are fairly tolerant of overclocking, all devices have finite limits. Generally, for any given voltage most parts will have a maximum "stable" speed where they still operate correctly. Past this speed, the device starts giving incorrect results, which can cause malfunctions and sporadic behavior in any system depending on it. While in a PC context, the usual result is a system crash, more subtle errors can go undetected, which over a long enough time can give unpleasant surprises such as [[data corruption]] (incorrectly calculated results, or worse ''writing to storage'' incorrectly) or the system failing only during certain specific tasks (general usage such as internet browsing and [[word processing]] appear fine, but any application wanting advanced graphics crashes the system. There might also be a chance for damage to the hardware itself).
 
At this point, an increase in operating voltage of a part may allow more headroom for further increases in clock speed, but the increased voltage can also significantly increase heat output, as well as shorten the lifespan further. At some point, there will be a limit imposed by the ability to supply the device with sufficient power, the user's ability to cool the part, and the device's own maximum voltage tolerance before it achieves [[Failure of electronic components|destructive failure]]. Overzealous use of voltage or inadequate cooling can rapidly degrade a device's performance to the point of failure, or in extreme cases outright [[Thermal runaway|destroy it]].
 
The speed gained by overclocking depends largely upon the applications and workloads being run on the system, and what components are being overclocked by the user; [[Benchmark (computing)|benchmark]]s for different purposes are published.


===Underclocking===
===Underclocking===
{{Main|Underclocking}}
{{Main|Underclocking}}
Conversely, the primary goal of [[underclocking]] is to reduce power consumption and the resultant heat generation of a device, with the trade-offs being lower clock speeds and reductions in performance. Reducing the cooling requirements needed to keep hardware at a given operational temperature has knock-on benefits such as lowering the number and speed of fans to allow [[Quiet PC|quieter operation]], and in mobile devices increase the length of battery life per charge. Some manufacturers underclock components of battery-powered equipment to improve battery life, or implement systems that detect when a device is operating under battery power and reduce clock frequency.<ref>{{cite web |title=What is an underclock? |url=https://www.lenovo.com/us/en/glossary/underclock/ |website=Lenovo |access-date=19 March 2025}}</ref>
Conversely, the primary goal of [[underclocking]] is to reduce power consumption and the resultant heat generation of a device, with the trade-offs being lower clock speeds and reductions in performance. Reducing the cooling requirements needed to keep hardware at a given operational temperature has knock-on benefits such as lowering the number and speed of fans to allow [[Quiet PC|quieter operation]], and in mobile devices increase the length of battery life per charge. Some manufacturers underclock components of battery-powered equipment to improve battery life, or implement systems that detect when a device is operating under battery power and reduce clock frequency.<ref>{{cite web |title=What is an underclock? |url=https://www.lenovo.com/us/en/glossary/underclock/ |website=Lenovo |access-date=19 March 2025}}</ref>


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===Components===
===Components===
{{Unreferenced section|date=October 2022}}
{{Empty section|date=August 2025}}
Technically any component that uses a timer (or clock) to synchronize its internal operations can be overclocked. Most efforts for computer components however focus on specific components, such as, [[Central processing unit|processors]] (a.k.a. CPU), [[video card]]s, [[motherboard]] [[chipset]]s, and [[random-access memory|RAM]]. Most modern processors derive their effective operating speeds by multiplying a base clock (processor bus speed) by an internal multiplier within the processor (the [[CPU multiplier]]) to attain their final speed.
 
Computer processors generally are overclocked by manipulating the [[CPU multiplier]] if that option is available, but the processor and other components can also be overclocked by increasing the base speed of the [[front-side bus|bus clock]]. Some systems allow additional tuning of other clocks (such as a [[Clock rate|system clock]]) that influence the bus clock speed that, again is multiplied by the processor to allow for finer adjustments of the final processor speed.
 
Most [[OEM systems]] do not expose to the user the adjustments needed to change processor clock speed or voltage in the BIOS of the OEM's motherboard, which precludes overclocking (for warranty and support reasons). The same processor installed on a different motherboard offering adjustments will allow the user to change them.
 
Any given component will ultimately stop operating reliably past a certain clock speed. Components will generally show some sort of malfunctioning behavior or other indication of compromised stability that alerts the user that a given speed is not stable, but there is always a possibility that a component will permanently fail without warning, even if voltages are kept within some pre-determined safe values. The maximum speed is determined by overclocking to the point of first instability, then accepting the last stable slower setting. Components are only guaranteed to operate correctly up to their rated values; beyond that different samples may have different overclocking potential. The end-point of a given overclock is determined by parameters such as available CPU multipliers, bus dividers, [[voltage]]s; the user's ability to manage thermal loads, cooling techniques; and several other factors of the individual devices themselves such as semiconductor clock and thermal tolerances, interaction with other components and the rest of the system.
 
==Considerations==
There are several things to be considered when overclocking. First is to ensure that the component is supplied with adequate power at a voltage sufficient to operate at the new [[clock rate]]. Supplying the power with improper settings or applying excessive [[voltage]] can permanently damage a component.
 
In a professional production environment, overclocking is only likely to be used where the increase in speed justifies the cost of the expert support required, the possibly reduced reliability, the consequent effect on maintenance contracts and warranties, and the higher power consumption. If faster speed is required it is often cheaper when all costs are considered to buy faster hardware.


==Factors==
=== Cooling ===
=== Cooling ===
{{Main|Computer cooling}}
{{Main|Computer cooling}}
[[Image:Copper heat sink with pipes.jpg|thumb|High quality [[heat sink]]s are often made of [[copper]].]]


All [[Electrical network|electronic circuits]] produce heat generated by the movement of electric current. As clock frequencies in [[digital circuit]]s and voltage applied increase, the heat generated by components running at the higher performance levels also increases. The relationship between clock frequencies and [[thermal design power]] (TDP) are linear. However, there is a limit to the maximum frequency which is called a "wall". To overcome this issue, overclockers raise the chip voltage to increase the overclocking potential. Voltage increases power consumption and consequently heat generation significantly (proportionally to the square of the voltage in a linear circuit, for example); this requires more cooling to avoid damaging the hardware by overheating. In addition, some digital circuits slow down at high temperatures due to changes in [[MOSFET]] device characteristics. Conversely, the overclocker may decide to ''decrease'' the chip voltage while overclocking (a process known as undervolting), to reduce heat emissions while performance remains optimal.
[[Image:Copper heat sink with pipes.jpg|thumb|High-quality [[heat sink]]s are often made of [[copper]].]]
 
While stock cooling systems are commonly designed for heat produced during non-overclocked use, they may not be adequate for overclocked parts. These may include the use of additional and more powerful [[fan (mechanical)|fans]], larger and more efficient [[heat sink]]s, [[heat pipe]]s, or the use of [[water cooling]].  


Stock cooling systems are designed for the amount of power produced during non-overclocked use; overclocked circuits can require more cooling, such as by powerful [[fan (mechanical)|fans]], larger [[heat sink]]s, [[heat pipe]]s and [[water cooling]]. Mass, 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.<ref name=Wainner38>{{cite book | title = The Book of Overclocking | first1 = Scott | last1 = Wainner | first2 = Robert |last2=Richmond | page = [https://archive.org/details/bookofoverclocki0000wain/page/38 38] | isbn = 978-1-886411-76-0 | publisher = No Starch Press | year = 2003 | url = https://archive.org/details/bookofoverclocki0000wain/page/38 }}</ref> [[Aluminium]] is more widely used; it has good thermal characteristics, though not as good as copper, and is significantly cheaper. Cheaper materials such as steel do not have good thermal characteristics. [[Heat pipe]]s can be used to improve conductivity. Many heatsinks combine two or more materials to achieve a balance between performance and cost.<ref name=Wainner38/>
==== Heat sinks ====
{{Main|Heat sink}}
Heat sinks are passive [[Heat exchanger|heat exchangers]] designed to take away excessive heat generated by the device it is in physical contact with. They are commonly made with [[copper]] or [[Aluminium|aluminum]], with copper having higher [[thermal conductivity]], and aluminum being less effcient but also cheaper.<ref name="Wainner38">{{cite book | title = The Book of Overclocking | first1 = Scott | last1 = Wainner | first2 = Robert |last2=Richmond | page = [https://archive.org/details/bookofoverclocki0000wain/page/38 38] | isbn = 978-1-886411-76-0 | publisher = No Starch Press | year = 2003 | url = https://archive.org/details/bookofoverclocki0000wain/page/38 }}</ref> [[Heat pipe]]s can be used to improve conductivity. Many heatsinks combine two or more materials to achieve a balance between performance and cost.<ref name="Wainner38" />


[[File:DIY PC watercooling T-Line.JPG|Interior of a water-cooled computer, showing CPU [[water block]], tubing, and pump|left|thumb]]
[[File:DIY PC watercooling T-Line.JPG|Interior of a water-cooled computer, showing CPU [[water block]], tubing, and pump|left|thumb]]
Water cooling carries [[waste heat]] to a [[radiator]]. [[Thermoelectric cooling]] devices which actually refrigerate using the [[Peltier effect]] can help with high [[thermal design power]] (TDP) processors made by Intel and AMD in the early twenty-first century. Thermoelectric cooling devices create temperature differences between two plates by running an [[electric current]] through the plates. This method of cooling is highly effective, but itself generates significant heat elsewhere which must be carried away, often by a convection-based heatsink or a [[water cooling#Computer usage|water cooling]] system.


[[Image:2007TaipeiITMonth IntelOCLiveTest Overclocking-6.jpg|right|thumb|[[Liquid nitrogen]] may be used for cooling an overclocked system, when an extreme measure of cooling is needed.]]
[[Image:2007TaipeiITMonth IntelOCLiveTest Overclocking-6.jpg|right|thumb|[[Liquid nitrogen]] may be used for cooling an overclocked system, when an extreme measure of cooling is needed.]]
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Submersion cooling, used by the [[Cray-2]] [[supercomputer]], involves sinking a part of computer system directly into a chilled liquid that is thermally conductive but has low [[electrical conductivity]]. The advantage of this technique is that no condensation can form on components.<ref name=Wainner48/> A good submersion liquid is [[Fluorinert]] made by [[3M]], which is expensive. Another option is [[mineral oil]], but impurities such as those in water might cause it to conduct electricity.<ref name=Wainner48>{{cite book | title = The Book of Overclocking | first = Scott | last = Wainner | author2 = Robert Richmond | page = [https://archive.org/details/bookofoverclocki0000wain/page/48 48] | isbn = 978-1-886411-76-0 | publisher = No Starch Press | year = 2003 | url = https://archive.org/details/bookofoverclocki0000wain/page/48 }}</ref>
Submersion cooling, used by the [[Cray-2]] [[supercomputer]], involves sinking a part of computer system directly into a chilled liquid that is thermally conductive but has low [[electrical conductivity]]. The advantage of this technique is that no condensation can form on components.<ref name=Wainner48/> A good submersion liquid is [[Fluorinert]] made by [[3M]], which is expensive. Another option is [[mineral oil]], but impurities such as those in water might cause it to conduct electricity.<ref name=Wainner48>{{cite book | title = The Book of Overclocking | first = Scott | last = Wainner | author2 = Robert Richmond | page = [https://archive.org/details/bookofoverclocki0000wain/page/48 48] | isbn = 978-1-886411-76-0 | publisher = No Starch Press | year = 2003 | url = https://archive.org/details/bookofoverclocki0000wain/page/48 }}</ref>


Amateur overclocking enthusiasts have used a mixture of [[dry ice]] and a solvent with a low freezing point, such as [[acetone]] or [[isopropyl alcohol]].<ref>{{cite web |url=https://www.techpowerup.com/forums/threads/overclocking-with-dry-ice.101545/ |title=overclocking with dry ice! |work=TechPowerUp Forums |date=August 13, 2009 |access-date=January 7, 2020 |archive-date=December 7, 2019 |archive-url=https://web.archive.org/web/20191207134408/https://www.techpowerup.com/forums/threads/overclocking-with-dry-ice.101545/ |url-status=live }}</ref> This [[cooling bath]], often used in laboratories, achieves a temperature of {{convert|−78|C}}.<ref>[http://chemwiki.ucdavis.edu/VV_Lab_Techniques/Cooling_baths Cooling baths – ChemWiki] {{Webarchive|url=https://web.archive.org/web/20120828144459/http://chemwiki.ucdavis.edu/VV_Lab_Techniques/Cooling_baths |date=2012-08-28 }}. Chemwiki.ucdavis.edu. Retrieved on 2013-06-17.</ref> However, this practice is discouraged due to its safety risks; the solvents are flammable and volatile, and dry ice can cause [[frostbite]] (through contact with exposed skin) and suffocation (due to the large volume of [[carbon dioxide]] generated when it sublimes).
Amateur overclocking enthusiasts have used a mixture of [[dry ice]] and a solvent with a low freezing point, such as [[acetone]] or [[isopropyl alcohol]].<ref>{{cite web |url=https://www.techpowerup.com/forums/threads/overclocking-with-dry-ice.101545/ |title=overclocking with dry ice! |work=TechPowerUp Forums |date=August 13, 2009 |access-date=January 7, 2020 |archive-date=December 7, 2019 |archive-url=https://web.archive.org/web/20191207134408/https://www.techpowerup.com/forums/threads/overclocking-with-dry-ice.101545/ |url-status=live }}</ref> This [[cooling bath]], often used in laboratories, achieves a temperature of {{convert|−78|C}}.<ref>[http://chemwiki.ucdavis.edu/VV_Lab_Techniques/Cooling_baths Cooling baths – ChemWiki] {{Webarchive|url=https://web.archive.org/web/20120828144459/http://chemwiki.ucdavis.edu/VV_Lab_Techniques/Cooling_baths|date=2012-08-28}}. Chemwiki.ucdavis.edu. Retrieved on 2013-06-17.</ref>


=== Stability and functional correctness ===
=== Stability and reliability ===


{{See also| Stress testing#Hardware }}
{{See also|Stress testing#Hardware}}


As an overclocked component operates outside of the manufacturer's recommended operating conditions, it may function incorrectly, leading to system instability. Another risk is [[Reliability, availability and serviceability (computer hardware)|silent data corruption]] by undetected errors. Such failures might never be correctly diagnosed and may instead be incorrectly attributed to software bugs in applications, [[device drivers]], 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.
As an overclocked component operates outside of the manufacturer's recommended operating conditions, it may function incorrectly, leading to system instability. Another risk is [[Reliability, availability and serviceability (computer hardware)|silent data corruption]] by undetected errors. Such failures might never be correctly diagnosed and may instead be incorrectly attributed to software bugs in applications, [[device drivers]], 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.
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A large-scale 2011 field study of hardware faults causing a system crash for consumer PCs and laptops showed a four to 20 times increase (depending on CPU manufacturer) in system crashes due to CPU failure for overclocked computers over an eight-month period.<ref>{{cite conference|url=http://research.microsoft.com/pubs/144888/eurosys84-nightingale.pdf|title=Cycles, cells and platters: an empirical analysis of hardware failures on a million consumer PCs.|conference=Proceedings of the sixth conference on Computer systems (EuroSys '11).|pages=343–356|year=2011|access-date=2012-12-05|archive-date=2012-11-14|archive-url=https://web.archive.org/web/20121114111006/http://research.microsoft.com/pubs/144888/eurosys84-nightingale.pdf|url-status=live}}</ref>
A large-scale 2011 field study of hardware faults causing a system crash for consumer PCs and laptops showed a four to 20 times increase (depending on CPU manufacturer) in system crashes due to CPU failure for overclocked computers over an eight-month period.<ref>{{cite conference|url=http://research.microsoft.com/pubs/144888/eurosys84-nightingale.pdf|title=Cycles, cells and platters: an empirical analysis of hardware failures on a million consumer PCs.|conference=Proceedings of the sixth conference on Computer systems (EuroSys '11).|pages=343–356|year=2011|access-date=2012-12-05|archive-date=2012-11-14|archive-url=https://web.archive.org/web/20121114111006/http://research.microsoft.com/pubs/144888/eurosys84-nightingale.pdf|url-status=live}}</ref>


In general, overclockers claim that testing can ensure that an overclocked system is stable and functioning correctly. Although software tools are available for testing hardware stability, it is generally impossible for any private individual to thoroughly test the functionality of a processor.<ref>{{cite journal | citeseerx = 10.1.1.62.9086 | title = Coverage Metrics for Functional Validation of Hardware Designs | publisher = IEEE Design & Test of Computers | year = 2001 | first1 = Serdar |last1=Tasiran |first2=Kurt |last2=Keutzer}}</ref> Achieving good [[fault coverage]] requires immense engineering effort; even with all of the resources dedicated to validation by manufacturers, faulty components and even design faults are not always detected.
In general, overclockers claim that testing can ensure that an overclocked system is stable and functioning correctly. Although software tools are available for testing hardware stability, it is generally impossible for any private individual to thoroughly test the functionality of a processor.<ref>{{cite journal | citeseerx = 10.1.1.62.9086 | title = Coverage Metrics for Functional Validation of Hardware Designs | journal = IEEE Design & Test of Computers | year = 2001 | first1 = Serdar |last1=Tasiran |first2=Kurt |last2=Keutzer | volume = 18 | issue = 4 | page = 36 | doi = 10.1109/54.936247 | bibcode = 2001IDTC...18...36T }}</ref>
 
A particular "stress test" can verify only the functionality of the specific instruction sequence used in combination with the data and may not detect faults in those operations. For example, an arithmetic operation may produce the correct result but incorrect [[status register|flags]]; if the flags are not checked, the error will go undetected.


To further complicate matters, in process technologies such as [[silicon on insulator]] (SOI), devices display [[hysteresis]]—a circuit's performance is affected by the events of the past, so without carefully targeted tests it is possible for a particular sequence of state changes to work at overclocked rates in one situation but not another even if the voltage and temperature are the same. Often, an overclocked system which passes stress tests experiences instabilities in other programs.<ref>{{cite web | url = http://blogs.msdn.com/oldnewthing/archive/2005/04/12/407562.aspx | first = Raymond | last = Chen | title = The Old New Thing: There's an awful lot of overclocking out there | date = April 12, 2005 | access-date = 2007-03-17 | archive-date = 2007-03-08 | archive-url = https://web.archive.org/web/20070308074036/http://blogs.msdn.com/oldnewthing/archive/2005/04/12/407562.aspx | url-status = dead }}</ref>
To further complicate matters, in process technologies such as [[silicon on insulator]] (SOI), devices display [[hysteresis]]—a circuit's performance is affected by the events of the past, so without carefully targeted tests it is possible for a particular sequence of state changes to work at overclocked rates in one situation but not another even if the voltage and temperature are the same. Often, an overclocked system which passes stress tests experiences instabilities in other programs.<ref>{{cite web | url = http://blogs.msdn.com/oldnewthing/archive/2005/04/12/407562.aspx | first = Raymond | last = Chen | title = The Old New Thing: There's an awful lot of overclocking out there | date = April 12, 2005 | access-date = 2007-03-17 | archive-date = 2007-03-08 | archive-url = https://web.archive.org/web/20070308074036/http://blogs.msdn.com/oldnewthing/archive/2005/04/12/407562.aspx | url-status = dead }}</ref>


In overclocking circles, "stress tests" or "torture tests" are used to check for correct operation of a component. These workloads are selected as they put a very high load on the component of interest (e.g. a graphically intensive application for testing video cards, or different math-intensive applications for testing general CPUs). Popular stress tests include [[Prime95]], [[Superpi]], OCCT, [[AIDA64]], [[Linpack]] (via the LinX and IntelBurnTest [[GUI]]s), SiSoftware Sandra, [[BOINC]], Intel Thermal Analysis Tool and [[Memtest86]]. The hope is that any functional-correctness issues with the overclocked component will manifest themselves during these tests, and if no errors are detected during the test, then the component is deemed "stable". Since fault coverage is important in [[Software testing|stability testing]], the tests are often run for long periods of time, hours or even days. An overclocked computer is sometimes described using the number of hours and the stability program used, such as "prime 12 hours stable".
=== Factors impacting overclocking potential ===
 
===Factors allowing overclocking===
Overclockability arises in part due to the economics of the manufacturing processes of CPUs and other components. In many cases components are manufactured by the same process, and tested after manufacture to determine their actual maximum ratings. Components are then marked with a rating chosen by the market needs of the semiconductor manufacturer. If [[Semiconductor device fabrication#Device test|manufacturing yield]] is high, more higher-rated components than required may be produced, and the manufacturer may mark and sell higher-performing components as lower-rated for marketing reasons. In some cases, the true maximum rating of the component may exceed even the highest rated component sold. Many devices sold with a lower rating may behave in all ways as higher-rated ones, while in the worst case operation at the higher rating may be more problematical.
Overclockability arises in part due to the economics of the manufacturing processes of CPUs and other components. In many cases components are manufactured by the same process, and tested after manufacture to determine their actual maximum ratings. Components are then marked with a rating chosen by the market needs of the semiconductor manufacturer. If [[Semiconductor device fabrication#Device test|manufacturing yield]] is high, more higher-rated components than required may be produced, and the manufacturer may mark and sell higher-performing components as lower-rated for marketing reasons. In some cases, the true maximum rating of the component may exceed even the highest rated component sold. Many devices sold with a lower rating may behave in all ways as higher-rated ones, while in the worst case operation at the higher rating may be more problematical.


Notably, higher clocks must always mean greater waste heat generation, as semiconductors set to high must dump to ground more often. In some cases, this means that the chief drawback of the overclocked part is far more heat dissipated than the maximums published by the manufacturer. Pentium architect [[Bob Colwell]] calls overclocking an "uncontrolled experiment in better-than-worst-case system operation".<ref>{{cite journal|first1=Bob|last1=Colwell|title=The Zen of Overclocking|journal=[[Computer (magazine)|Computer]]|volume=37|issue=3|date=March 2004|pages=9–12|publisher=[[Institute of Electrical and Electronics Engineers]]|doi=10.1109/MC.2004.1273994|s2cid=21582410}}</ref>
Notably, higher clocks must always mean greater waste heat generation, as semiconductors set to high must dump to ground more often. In some cases, this means that the chief drawback of the overclocked part is far more heat dissipated than the maximums published by the manufacturer. Pentium architect [[Bob Colwell]] calls overclocking an "uncontrolled experiment in better-than-worst-case system operation".<ref>{{cite journal|first1=Bob|last1=Colwell|title=The Zen of Overclocking|journal=[[Computer (magazine)|Computer]]|volume=37|issue=3|date=March 2004|pages=9–12|publisher=[[Institute of Electrical and Electronics Engineers]]|doi=10.1109/MC.2004.1273994|bibcode=2004Compr..37c...9C |s2cid=21582410}}</ref>


=== Measuring effects of overclocking ===
=== Effects ===
{{Unreferenced section|date=October 2022}}
{{Empty section|date=August 2025}}
[[Benchmark (computing)|Benchmarks]] are used to evaluate performance, and they can 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 the 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). A widely used test of stability is Prime95, which has built-in error checking that fails if the computer is unstable.
 
Using only the benchmark scores, it may be difficult to judge the difference overclocking makes to the overall performance of a computer. For example, some benchmarks test only one aspect of the system, such as memory [[Bandwidth (computing)|bandwidth]], without taking into consideration how higher [[clock rate]]s in this aspect will improve the system performance as a whole. Apart from demanding applications such as video encoding, high-demand [[database]]s and [[scientific computing]], [[memory bandwidth]] is typically not a [[bottleneck (engineering)|bottleneck]], so a great increase in memory bandwidth may be unnoticeable to a user depending on the applications used. Other benchmarks, such as [[3D Mark|3DMark]], attempt to replicate game conditions.


== Manufacturer and vendor overclocking ==
== Manufacturer and vendor overclocking ==
Line 102: Line 79:


== CPU multiplier locking ==
== CPU multiplier locking ==
{{unreferenced section|date=December 2020}}
{{Empty section|date=August 2025}}
'''CPU multiplier locking''' is the process of permanently setting a [[Central processing unit|CPU]]'s [[clock multiplier]]. [[AMD]] CPUs are unlocked in early editions of a model and locked in later editions, but nearly all [[Intel]] CPUs are locked and recent{{when|date=December 2020}} models are very resistant to unlocking to prevent overclocking by users. AMD ships unlocked CPUs with their [[Opteron]], [[AMD FX|FX]], All [[Ryzen]] desktop chips (except 3D variants) and Black Series line-up, while Intel uses the [[wikt:moniker|moniker]]s of "Extreme Edition" and "K-Series." Intel usually has one or two Extreme Edition CPUs on the market as well as X series and K series CPUs analogous to AMD's Black Edition. AMD has the majority of their desktop range in a Black Edition.
 
Users usually unlock CPUs to allow overclocking, but sometimes to allow for [[underclocking]] in order to maintain the [[front side bus]] speed (on older CPUs) compatibility with certain motherboards. Unlocking generally invalidates the manufacturer's warranty, and mistakes can cripple or destroy a CPU. Locking a chip's clock multiplier does not necessarily prevent users from overclocking, as the speed of the front-side bus or PCI multiplier (on newer CPUs) may still be changed to provide a performance increase. AMD [[Athlon]] and [[Athlon XP]] CPUs are generally unlocked by connecting bridges ([[jumper (computing)|jumper]]-like points) on the top of the CPU with [[electrical conduction|conductive]] paint or [[Graphite|pencil lead]]. Other CPU models may require different procedures.
 
Increasing front-side bus or northbridge/PCI clocks can overclock locked CPUs, but this throws many system frequencies out of sync, since the RAM and PCI frequencies are modified as well.
 
Contrary to popular belief, the "pin mod" method which claims to unlock older AMD Athlon XP CPUs does not work. All other unlocked processors from LGA1151 and v2 (including 7th, 8th, and 9th generation) and BGA1440 allow for BCLK overclocking (as long as the OEM allows it), while all other locked processors from 7th, 8th, and 9th gen were not able to go past 102.7&nbsp;MHz. 10th gen however, could reach 103&nbsp;MHz <ref>{{Cite web|url=https://www.techpowerup.com/review/intel-core-i5-10400f/|title=Intel Core i5-10400F Review – Six Cores with HT for Under $200|website=TechPowerUp|date=May 28, 2020 |access-date=2021-12-15|archive-date=2021-12-15|archive-url=https://web.archive.org/web/20211215020857/https://www.techpowerup.com/review/intel-core-i5-10400f/|url-status=live}}</ref> on the BCLK.


== Advantages ==
== Advantages ==
 
{{Empty section|date=August 2025}}
{{Original research|section|date=December 2011}}
* Higher '''performance''' in games, en-/decoding, video editing and system tasks at no additional direct monetary expense, but with increased electrical consumption and thermal output.
* System '''optimization''': Some systems have "[[Bottleneck (software)|bottlenecks]]", where small overclocking of one component can help realize the full potential of another component to a greater percentage than when just the limiting hardware itself is overclocked. For instance: many [[motherboard]]s with [[Athlon 64|AMD Athlon 64]] processors limit the clock rate of four units of RAM to 333 [[Hertz|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&nbsp;GHz is most likely 9×200&nbsp;MHz) by a fixed [[integer]] such that, at a stock clock rate, the RAM would run at a clock rate near 333&nbsp;MHz. Manipulating elements of how the processor clock rate is set (usually adjusting the multiplier), it is often possible to overclock the processor a small amount, around 5–10%, and gain a small increase in RAM clock rate and/or reduction in RAM latency timings.
* It can be '''cheaper''' to purchase a lower performance component and overclock it to the clock rate of a more expensive component.
* '''Extending''' the practical service life of old or obsolete equipment.
* If done via methods what allow to change [[clock rate]] "on the fly", it gains versatility. So, for example - overclock computer where lots of computing power is needed '''right now''', and put it back to normal [[clock rate]] once task is done or computers starts getting too hot - then, wait to cool back, and overclock again, etc.


==Disadvantages==
==Disadvantages==


=== General ===
=== Noise ===
{{See also|Health effects from noise}}
Fans running at higher speeds generate additional [[noise]]. The increased heat output from a overclocked device might require faster-spinning fans to be adequately cooled. Depending on the speed, model and numbers of fans used, these noise can reach 50&nbsp;[[Decibel#Acoustics|dB]] or higher, causing [[annoyance]] or even [[mental distress]]. Fan noise has been found to be roughly proportional to the [[Fifth power (algebra)|fifth power]] of fan speed, and halving speed reduces noise by about 15&nbsp;[[Sound pressure#Sound pressure level|dB]].<ref>{{Cite web |title=UK Health and Safety Executive: Top 10 noise control techniques |url=http://www.hse.gov.uk/pubns/top10noise.pdf |url-status=live |archive-url=https://web.archive.org/web/20191126163348/http://www.hse.gov.uk/pubns/top10noise.pdf |archive-date=2019-11-26 |access-date=2011-12-30}}</ref>


{{Original research|section|date=December 2011}}
=== Reliability ===
* Higher [[clock rate]]s and voltages increase '''power consumption''', also increasing '''electricity cost''' and '''heat production'''. The additional heat increases the ambient air temperature within the system case, which may affect other components. The hot air blown out of the case heats the room it's in.
An overclocked computer may suffer from instability and behave erratically. This can include inconsistent performance ([[CPU throttling|throttling]]), abrupt shutdown and reboots due to [[Computer cooling#Damage prevention|overheat]], [[overvoltage]] or [[overcurrent]], [[Data loss|data lost]] and [[data corruption]].
* Fan '''noise''': High-performance fans running at maximum speed used for the required degree of cooling of an overclocked machine can be noisy, some producing 50&nbsp;[[Decibel#Acoustics|dB]] or more of noise. When maximum cooling is not required, in any equipment, fan speeds can be reduced below the maximum: fan noise has been found to be roughly proportional to the fifth power of fan speed; halving speed reduces noise by about 15&nbsp;dB.<ref>{{Cite web|url=http://www.hse.gov.uk/pubns/top10noise.pdf|title=UK Health and Safety Executive: Top 10 noise control techniques|access-date=2011-12-30|archive-date=2019-11-26|archive-url=https://web.archive.org/web/20191126163348/http://www.hse.gov.uk/pubns/top10noise.pdf|url-status=live}}</ref> Fan noise can be reduced by design improvements, e.g. with aerodynamically optimized blades for smoother airflow, reducing noise to around 20&nbsp;dB at approximately 1 metre{{Citation needed|date=December 2011}} or larger fans rotating more slowly, which produce less noise than smaller, faster fans with the same airflow. Acoustical insulation inside the case e.g. acoustic foam can reduce noise. Additional cooling methods which do not use fans can be used, such as liquid and phase-change cooling.
* An overclocked computer may become '''unreliable'''. For example: [[Microsoft Windows]] may appear to work with no problems, but when it is re-installed or upgraded, error messages may be received such as a "file copy error" during Windows Setup.<ref>{{Cite web|url=http://support.microsoft.com/kb/310064/en-us|title=Article ID: 310064 – Last Review: May 7, 2007 – Revision: 6.2 How to troubleshoot problems during installation when you upgrade from Windows 98 or Windows Millennium Edition to Windows XP|access-date=September 4, 2008|archive-date=May 15, 2009|archive-url=https://web.archive.org/web/20090515131653/http://support.microsoft.com/kb/310064/EN-US|url-status=live}}</ref> Because installing an [[operating system]] is very memory-intensive, decoding errors may occur when files are extracted.
* The '''lifespan''' of semiconductor components may be reduced by increased voltages and heat.
* Warranties may be voided by overclocking.


=== Risks of overclocking ===
=== Hardware damage ===
 
Increasing the operation frequency of a component will usually increase its thermal output in a linear fashion, while an increase in voltage usually causes thermal power to increase quadratically.<ref>{{Cite book |last=Darche |first=Philippe |url=https://books.google.com/books?id=XeQGEAAAQBAJ&dq=power+wall+&pg=PA128 |title=Microprocessor 3: Core Concepts – Hardware Aspects |date=2020-11-02 |publisher=John Wiley & Sons |isbn=978-1-119-78800-3 |language=en}}</ref>
* Increasing the operation frequency of a component will usually increase its thermal output in a linear fashion, while an increase in voltage usually causes thermal power to increase quadratically.<ref>{{Cite book |last=Darche |first=Philippe |url=https://books.google.com/books?id=XeQGEAAAQBAJ&dq=power+wall+&pg=PA128 |title=Microprocessor 3: Core Concepts – Hardware Aspects |date=2020-11-02 |publisher=John Wiley & Sons |isbn=978-1-119-78800-3 |language=en}}</ref> Excessive voltages or improper cooling may cause chip temperatures to rise to dangerous levels, causing the chip to be damaged or destroyed.
* Exotic cooling methods used to facilitate overclocking such as water cooling are more likely to cause damage if they malfunction. Sub-ambient cooling methods such as [[Computer cooling#Phase-change cooling|phase-change cooling]] or [[liquid nitrogen]] will cause water [[condensation]], which will cause electrical damage unless controlled; some methods include using kneaded erasers or shop towels to catch the condensation.


=== Limitations ===
=== Limitations ===
 
{{Empty section|date=August 2025}}
Overclocking components can only be of noticeable benefit if the component is on the [[Critical path method|critical path]] for a process, if it is a bottleneck. If disk access or the speed of an [[Internet]] connection limit the speed of a process, a 20% increase in processor speed is unlikely to be noticed, however there are some scenarios where increasing the clock speed of a processor actually allows an SSD to be read and written to faster. Overclocking a CPU will not noticeably benefit a game when a graphics card's performance is the "bottleneck" of the game.


=== Adaptive Management in Overclocking ===
=== Adaptive Management in Overclocking ===
 
{{Empty section|date=August 2025}}
Similar to dynamic adjustments critical in network management for handling data flow and preventing bottlenecks, overclocking computer hardware requires ongoing monitoring and adaptations to maintain system stability and performance. In high-performance network systems, researchers like Åkerblom et al. (2023) have developed adaptive methods such as Thompson Sampling to optimize system responses under varying conditions, analogous to technologies used in overclocking like real-time voltage adjustments and adaptive cooling systems. These technologies are crucial in managing the additional heat and power demands imposed by overclocked components, ensuring that the hardware operates within safe temperature and voltage limits to prevent damage and prolong the lifespan of the components[1].
 


== Graphics cards ==
== Graphics cards ==


[[File:Bfg geforce 6800 gs oc.jpg|thumb|200px|right|The BFG GeForce 6800GSOC ships with higher memory and [[clock rate]]s than the standard 6800GS.]]
[[File:Bfg geforce 6800 gs oc.jpg|thumb|200px|right|The BFG GeForce 6800GSOC ships with higher memory and [[clock rate]]s than the standard 6800GS.]]
Graphics cards can also be overclocked. There are [[utility software|utilities]] to achieve this, such as [[EVGA Corporation|EVGA]]'s Precision, [[RivaTuner]], [[Advanced Micro Devices|AMD]] Overdrive (on [[Advanced Micro Devices|AMD]] cards only), [[Micro-Star International|MSI]] Afterburner, Zotac Firestorm, and the PEG Link Mode on [[Asus]] [[motherboard]]s. Overclocking a GPU will often yield a marked increase in performance in synthetic benchmarks, usually reflected in game performance.<ref>{{Cite web |url=http://www.altesc.net/2013/06/15/gtx-780-overclocking/ |title=Alt+Esc {{!}} GTX 780 Overclocking Guide<!-- Bot generated title --> |work=Alt+Esc |access-date=2013-06-18 |archive-date=2013-06-24 |archive-url=https://web.archive.org/web/20130624231537/http://www.altesc.net/2013/06/15/gtx-780-overclocking/ |url-status=live }}</ref> It is sometimes possible to see that a graphics card is being pushed beyond its limits before any permanent damage is done by observing on-screen artifacts or unexpected system crashes. It is common to run into one of those problems when overclocking graphics cards; both symptoms at the same time usually means that the card is severely pushed beyond its heat, [[clock rate]], and/or voltage limits, however if seen when not overclocked, they indicate a faulty card. After a reboot, video settings are reset to standard values stored in the graphics card firmware, and the maximum [[clock rate]] of that specific card is now deducted.
Graphics cards can also be overclocked. There are [[utility software|utilities]] to achieve this, such as [[EVGA Corporation|EVGA]]'s Precision, [[RivaTuner]], [[Advanced Micro Devices|AMD]] Overdrive (on [[Advanced Micro Devices|AMD]] cards only), [[Micro-Star International|MSI]] Afterburner, Zotac Firestorm, and the PEG Link Mode on [[Asus]] [[motherboard]]s. Overclocking a GPU will often yield a marked increase in performance in synthetic benchmarks, usually reflected in game performance.<ref>{{Cite web |url=http://www.altesc.net/2013/06/15/gtx-780-overclocking/ |title=Alt+Esc {{!}} GTX 780 Overclocking Guide<!-- Bot generated title --> |work=Alt+Esc |access-date=2013-06-18 |archive-date=2013-06-24 |archive-url=https://web.archive.org/web/20130624231537/http://www.altesc.net/2013/06/15/gtx-780-overclocking/ |url-status=live }}</ref>
 
Some overclockers apply a [[potentiometer]] to the graphics card to manually adjust the voltage (which usually invalidates the warranty). This allows for finer adjustments, as overclocking software for graphics cards can only go so far. Excessive voltage increases may damage or destroy components on the graphics card or the entire graphics card itself (practically speaking).


== Flashing ==
== Flashing ==
{{Unreferenced section|date=October 2022}}
{{Empty section|date=August 2025}}
=== Alternatives ===
 
Flashing and unlocking can be used to improve the performance of a [[Graphics card|video card]], without technically overclocking (but is much riskier than overclocking just through software).
 
'''''Flashing''''' refers to using the [[firmware]] of a different card with the same (or sometimes similar) core and compatible firmware, effectively making it a higher model card; it can be difficult, and may be irreversible. Sometimes [[Computer software|standalone software]] to modify the firmware files can be found, e.g. [[NiBiTor]] (GeForce 6/7 series are well regarded in this aspect), without using firmware for a better model video card. For example, video cards with 3D accelerators (most, {{As of|2011|lc=on}}) have two voltage and [[clock rate]] settings, one for 2D and one for 3D, but were designed to operate with ''three'' voltage stages, the third being somewhere between the aforementioned two, serving as a fallback when the card overheats or as a middle-stage when going from 2D to 3D operation mode. Therefore, it could be wise to set this middle-stage prior to "serious" overclocking, specifically because of this fallback ability; the card can drop down to this [[clock rate]], reducing by a few (or sometimes a few dozen, depending on the setting) percent of its efficiency and cool down, without dropping out of 3D mode (and afterwards return to the desired high performance clock and voltage settings).
 
Some cards have abilities not directly connected with overclocking. For example, Nvidia's [[GeForce|GeForce 6600GT]] (AGP flavor) has a temperature monitor used internally by the card, invisible to the user if standard firmware is used. Modifying the firmware can display a 'Temperature' tab.
 
'''''Unlocking''''' refers to enabling extra [[Graphics pipeline|pipelines]] or [[pixel shader]]s. The [[GeForce 6 series|6800LE]], the [[GeForce 6 series|6800GS]] and [[GeForce 6 series|6800]] ([[Accelerated Graphics Port|AGP]] models only) were some of the first cards to benefit from unlocking. While these models have either 8 or 12 pipes enabled, they share the same 16x6 [[Graphics processing unit|GPU]] core as a [[GeForce 6 series|6800GT]] or Ultra, but pipelines and shaders beyond those specified are disabled; the GPU may be fully functional, or may have been found to have faults which do not affect operation at the lower specification. GPUs found to be fully functional can be unlocked successfully, although it is not possible to be sure that there are undiscovered faults; in the worst case the card may become [[Brick (electronics)|permanently unusable]].


== See also ==
== See also ==
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{{Div col|colwidth=20em}}
{{Div col|colwidth=20em}}
* [[Clock rate]]
* [[CPU-Z]]
* [[CPU-Z]]
* [[Double boot]]
* [[Double boot]]
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* [[Serial presence detect]] (SPD)
* [[Serial presence detect]] (SPD)
* [[Super PI]]
* [[Super PI]]
* [[Underclocking]]
* [[UNIVAC I#Instructions and data|UNIVAC I Overdrive, 1952 unofficial modification]]
* [[UNIVAC I#Instructions and data|UNIVAC I Overdrive, 1952 unofficial modification]]
{{div col end}}
{{div col end}}
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{{Reflist|33em}}
{{Reflist|33em}}
;Notes
;Notes
*{{cite journal | first = Bob | last = Colwell | author-link = Bob Colwell | title = The Zen of Overclocking | journal = Computer | volume = 37 | issue = 3 | pages = 9–12 |date=March 2004 | doi = 10.1109/MC.2004.1273994| s2cid = 21582410 }}
*{{cite journal | first = Bob | last = Colwell | author-link = Bob Colwell | title = The Zen of Overclocking | journal = Computer | volume = 37 | issue = 3 | pages = 9–12 |date=March 2004 | doi = 10.1109/MC.2004.1273994| bibcode = 2004Compr..37c...9C | s2cid = 21582410 }}
*{{Cite journal |last1=Åkerblom |first1=Niklas |last2=Hoseini |first2=Fazeleh Sadat |last3=Chehreghani |first3=Morteza Haghir |year=2023 |title=Online learning of network bottlenecks via minimax paths |journal=Machine Learning |volume=112 |pages=131–150 |doi=10.1007/s10994-022-06270-0|doi-access=free |arxiv=2109.08467 }}
*{{Cite journal |last1=Åkerblom |first1=Niklas |last2=Hoseini |first2=Fazeleh Sadat |last3=Chehreghani |first3=Morteza Haghir |year=2023 |title=Online learning of network bottlenecks via minimax paths |journal=Machine Learning |volume=112 |pages=131–150 |doi=10.1007/s10994-022-06270-0|doi-access=free |arxiv=2109.08467 }}


Revision as of 04:10, 17 November 2025

Template:Short description Template:Use American English Template:Use mdy dates

File:Overclock.jpg
A computer BIOS on an ABIT NF7-S motherboard with an overclocked AMD Athlon XP CPU, running at 2,442 MHz

In computing, overclocking is the practice of increasing the clock rate of a semiconductor device, such as a processor, beyond its rated speed, potentially increasing its performance.[1] Overclocked devices, however, may have shorter lifespans, become unstable and unreliable, and in extreme cases, be permanently damaged. Many manufacturers do not cover damage from overclocking in their warranties, while some allow it inside a predefined safety margin.

Overview

A semiconductor device's processing speed depends on a variety of factors, including, but not limited to, its clock speed, microarchitecture, the kind of software it's running, and the bandwidth, latency and size for each level of its memory. All else being equal, a faster-clocked device can, though not necessarily, perform faster. Operating voltage is often increased to maintain a component's operational stability at accelerated speeds. Operating at higher frequencies and voltages increase power consumption and heat.[2] Overclocking a device introduces additional risks of failure, for example, by overheating when the increased heat load is not removed,[2] or by the device requesting more power than its power supply can provide.Script error: No such module "Unsubst".

Underclocking

Script error: No such module "Labelled list hatnote".

Conversely, the primary goal of underclocking is to reduce power consumption and the resultant heat generation of a device, with the trade-offs being lower clock speeds and reductions in performance. Reducing the cooling requirements needed to keep hardware at a given operational temperature has knock-on benefits such as lowering the number and speed of fans to allow quieter operation, and in mobile devices increase the length of battery life per charge. Some manufacturers underclock components of battery-powered equipment to improve battery life, or implement systems that detect when a device is operating under battery power and reduce clock frequency.[3]

Underclocking and undervolting would be attempted on a desktop system to have it operate silently (such as for a home entertainment center) while potentially offering higher performance than currently offered by low-voltage processor offerings. This would use a "standard-voltage" part and attempt to run with lower voltages (while attempting to keep the desktop speeds) to meet an acceptable performance/noise target for the build. This was also attractive as using a "standard voltage" processor in a "low voltage" application avoided paying the traditional price premium for an officially certified low voltage version. However again like overclocking there is no guarantee of success, and the builder's time researching given system/processor combinations and especially the time and tedium of performing many iterations of stability testing need to be considered. The usefulness of underclocking (again like overclocking) is determined by what processor offerings, prices, and availability are at the specific time of the build. Underclocking is also sometimes used when troubleshooting.[4]

Enthusiast culture

Overclocking has become more accessible with motherboard makers offering overclocking as a marketing feature on their mainstream product lines. However, the practice is embraced more by enthusiasts than professional users, as overclocking carries a risk of reduced reliability, accuracy and damage to data and equipment. Additionally, most manufacturer warranties and service agreements do not cover overclocked components nor any incidental damages caused by their use. While overclocking can still be an option for increasing personal computing capacity, and thus workflow productivity for professional users, the importance of stability testing components thoroughly before employing them into a production environment cannot be overstated.

Overclocking offers several draws for overclocking enthusiasts. Overclocking allows testing of components at speeds not currently offered by the manufacturer, or at speeds only officially offered on specialized, higher-priced versions of the product. A general trend in the computing industry is that new technologies tend to debut in the high-end market first, then later trickle down to the performance and mainstream market. If the high-end part only differs by an increased clock speed, an enthusiast can attempt to overclock a mainstream part to simulate the high-end offering. This can give insight on how over-the-horizon technologies will perform before they are officially available on the mainstream market, which can be especially helpful for other users considering if they should plan ahead to purchase or upgrade to the new feature when it is officially released.

Some hobbyists enjoy building, tuning, and "Hot-Rodding" their systems in competitive benchmarking competitions, competing with other like-minded users for high scores in standardized computer benchmark suites. Others will purchase a low-cost model of a component in a given product line, and attempt to overclock that part to match a more expensive model's stock performance. Another approach is overclocking older components to attempt to keep pace with increasing system requirements and extend the useful service life of the older part or at least delay purchase of new hardware solely for performance reasons. Another rationale for overclocking older equipment is even if overclocking stresses equipment to the point of failure earlier, little is lost as it is already depreciated, and would have needed to be replaced in any case.[5]

Components

Template:Empty section

Factors

Cooling

Script error: No such module "Labelled list hatnote".

File:Copper heat sink with pipes.jpg
High-quality heat sinks are often made of copper.

While stock cooling systems are commonly designed for heat produced during non-overclocked use, they may not be adequate for overclocked parts. These may include the use of additional and more powerful fans, larger and more efficient heat sinks, heat pipes, or the use of water cooling.

Heat sinks

Script error: No such module "Labelled list hatnote". Heat sinks are passive heat exchangers designed to take away excessive heat generated by the device it is in physical contact with. They are commonly made with copper or aluminum, with copper having higher thermal conductivity, and aluminum being less effcient but also cheaper.[6] Heat pipes can be used to improve conductivity. Many heatsinks combine two or more materials to achieve a balance between performance and cost.[6]

File:DIY PC watercooling T-Line.JPG
Interior of a water-cooled computer, showing CPU water block, tubing, and pump
File:2007TaipeiITMonth IntelOCLiveTest Overclocking-6.jpg
Liquid nitrogen may be used for cooling an overclocked system, when an extreme measure of cooling is needed.

Other cooling methods are forced convection and phase transition cooling which is used in refrigerators and can be adapted for computer use. Liquid nitrogen, liquid helium, and dry ice are used as coolants in extreme cases,[7] such as record-setting attempts or one-off experiments rather than cooling an everyday system. In June 2006, IBM and Georgia Institute of Technology jointly announced a new record in silicon-based chip clock rate (the rate a transistor can be switched at, not the CPU clock rate[8]) above 500 GHz, which was done by cooling the chip to Script error: No such module "convert". using liquid helium.[9] Set in November 2012, the CPU Frequency World Record is 9008.82 MHz as of December 2022.[10] These extreme methods are generally impractical in the long term, as they require refilling reservoirs of vaporizing coolant, and condensation can form on chilled components.[7] Moreover, silicon-based junction gate field-effect transistors (JFET) will degrade below temperatures of roughly Script error: No such module "convert". and eventually cease to function or "freeze out" at Script error: No such module "convert". since the silicon ceases to be semiconducting,[11] so using extremely cold coolants may cause devices to fail. Blowtorch is used to temporarily raise temperature to issues of over-cooling when not desirable.[12][13]

Submersion cooling, used by the Cray-2 supercomputer, involves sinking a part of computer system directly into a chilled liquid that is thermally conductive but has low electrical conductivity. The advantage of this technique is that no condensation can form on components.[14] A good submersion liquid is Fluorinert made by 3M, which is expensive. Another option is mineral oil, but impurities such as those in water might cause it to conduct electricity.[14]

Amateur overclocking enthusiasts have used a mixture of dry ice and a solvent with a low freezing point, such as acetone or isopropyl alcohol.[15] This cooling bath, often used in laboratories, achieves a temperature of Script error: No such module "convert"..[16]

Stability and reliability

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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, device drivers, 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.

A large-scale 2011 field study of hardware faults causing a system crash for consumer PCs and laptops showed a four to 20 times increase (depending on CPU manufacturer) in system crashes due to CPU failure for overclocked computers over an eight-month period.[17]

In general, overclockers claim that testing can ensure that an overclocked system is stable and functioning correctly. Although software tools are available for testing hardware stability, it is generally impossible for any private individual to thoroughly test the functionality of a processor.[18]

To further complicate matters, in process technologies such as silicon on insulator (SOI), devices display hysteresis—a circuit's performance is affected by the events of the past, so without carefully targeted tests it is possible for a particular sequence of state changes to work at overclocked rates in one situation but not another even if the voltage and temperature are the same. Often, an overclocked system which passes stress tests experiences instabilities in other programs.[19]

Factors impacting overclocking potential

Overclockability arises in part due to the economics of the manufacturing processes of CPUs and other components. In many cases components are manufactured by the same process, and tested after manufacture to determine their actual maximum ratings. Components are then marked with a rating chosen by the market needs of the semiconductor manufacturer. If manufacturing yield is high, more higher-rated components than required may be produced, and the manufacturer may mark and sell higher-performing components as lower-rated for marketing reasons. In some cases, the true maximum rating of the component may exceed even the highest rated component sold. Many devices sold with a lower rating may behave in all ways as higher-rated ones, while in the worst case operation at the higher rating may be more problematical.

Notably, higher clocks must always mean greater waste heat generation, as semiconductors set to high must dump to ground more often. In some cases, this means that the chief drawback of the overclocked part is far more heat dissipated than the maximums published by the manufacturer. Pentium architect Bob Colwell calls overclocking an "uncontrolled experiment in better-than-worst-case system operation".[20]

Effects

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Manufacturer and vendor overclocking

Overclocking is sometimes offered as a legitimate service or feature for consumers, in which a manufacturer or retailer tests the overclocking capability of processors, memory, video cards, and other hardware products. Several video card manufactures now offer factory-overclocked versions of their graphics accelerators, complete with a warranty, usually at a price intermediate between that of the standard product and a non-overclocked product of higher performance.

It is speculated that manufacturers implement overclocking prevention mechanisms such as CPU multiplier locking to prevent users from buying lower-priced items and overclocking them. These measures are sometimes marketed as a consumer protection benefit, but are often criticized by buyers.

Many motherboards are sold, and advertised, with extensive facilities for overclocking implemented in hardware and controlled by BIOS settings.[21]

CPU multiplier locking

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Advantages

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Disadvantages

Noise

Script error: No such module "Labelled list hatnote". Fans running at higher speeds generate additional noise. The increased heat output from a overclocked device might require faster-spinning fans to be adequately cooled. Depending on the speed, model and numbers of fans used, these noise can reach 50 dB or higher, causing annoyance or even mental distress. Fan noise has been found to be roughly proportional to the fifth power of fan speed, and halving speed reduces noise by about 15 dB.[22]

Reliability

An overclocked computer may suffer from instability and behave erratically. This can include inconsistent performance (throttling), abrupt shutdown and reboots due to overheat, overvoltage or overcurrent, data lost and data corruption.

Hardware damage

Increasing the operation frequency of a component will usually increase its thermal output in a linear fashion, while an increase in voltage usually causes thermal power to increase quadratically.[23]

Limitations

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Adaptive Management in Overclocking

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Graphics cards

File:Bfg geforce 6800 gs oc.jpg
The BFG GeForce 6800GSOC ships with higher memory and clock rates than the standard 6800GS.

Graphics cards can also be overclocked. There are utilities to achieve this, such as EVGA's Precision, RivaTuner, AMD Overdrive (on AMD cards only), MSI Afterburner, Zotac Firestorm, and the PEG Link Mode on Asus motherboards. Overclocking a GPU will often yield a marked increase in performance in synthetic benchmarks, usually reflected in game performance.[24]

Flashing

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See also

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References

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  14. ↑ a b Script error: No such module "citation/CS1".
  15. ↑ Script error: No such module "citation/CS1".
  16. ↑ Cooling baths – ChemWiki Template:Webarchive. Chemwiki.ucdavis.edu. Retrieved on 2013-06-17.
  17. ↑ Script error: No such module "citation/CS1".
  18. ↑ Script error: No such module "Citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".
  20. ↑ Script error: No such module "Citation/CS1".
  21. ↑ Script error: No such module "citation/CS1".
  22. ↑ Script error: No such module "citation/CS1".
  23. ↑ Script error: No such module "citation/CS1".
  24. ↑ Script error: No such module "citation/CS1".

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Notes
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External links

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Overclocking and benchmark databases

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