Overclocking
Encyclopedia
Overclocking is the process of operating a computer component
at a higher clock rate
(more clock cycles per second) than it was designed for or was specified by the manufacturer, but some manufacturers purposely underclock their components to improve battery life. Many people just overclock or 'rightclock' their hardware to improve their performance. This is practiced more by enthusiasts than professional users seeking an increase in the performance of their computers, as overclocking carries risks of less reliable functioning and damage. There are several purposes for overclocking: for professional users overclocking allows pushing the boundary of professional personal computing capacity therefore allowing improved productivity or allows testing over-the-horizon technologies beyond that possible with the available component specifications before entering the specialized computing realm and pricing - this leverages the manufacturing practice to specify components to a level that optimizes yield and profit margin, some components are capable of more; there are also hobbyists that, like car enthusiasts, enjoy building, tuning, and comparison racing their systems with standardized benchmark software. Some hobbyists purchase less expensive computer components and overclock to higher clock rates in an attempt to save money but achieve the same performance. A similar but slightly different approach to cost saving is overclocking outdated components to keep pace with new system requirements
, rather than purchasing new hardware. This approach lowers the cost of a failure since the system is fully depreciated and new system is needed anyways.;
People who overclock their components mainly focus their efforts on processors
, video card
s, motherboard
chipset
s, and RAM
. It is done through manipulating the CPU multiplier
and the rate of the external clock (such as a front-side bus (FSB) clock) until a maximum stable operating frequency is reached. While the idea is simple, variation in the electrical and physical characteristics of computing systems complicates the process. Power consumption of digital circuits often increases with frequency or clocking speed. The high-frequency operation of semiconductor device
s as used in computers to a certain extent improves with an increase in voltage; but operation at high speed and increased voltage increases power dissipation
and heating. Overheating caused by higher dissipation, and operation at higher voltage regardless of power, can cause malfunctioning or permanent damage. Increasing voltage supplied and improving cooling can increase the maximum stable operating speed, subject to these risks.
CPU multipliers, bus dividers, voltage
s, thermal loads, cooling techniques and several other factors such as individual semiconductor clock and thermal tolerances can affect the performance of the computer.
. 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 have built-in overclocking capabilities. Motherboards with fewer features, such as those found in original equipment manufacturer
(OEM) systems, often do not support overclocking.
All electronic circuits
produce heat generated by the movement of electrical 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 will raise power consumption exponentially however, and in turn the amount of power that must be dissipated. 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 MOSFET
device characteristics.
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 heat sink
s, heat pipe
s 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 pipe
s are commonly used to improve conductivity. Many heatsinks combine two or more materials to achieve a balance between performance and cost.
Water cooling carries waste heat
to a radiator. Thermoelectric cooling
devices, also known as Peltier devices, are recently popular with the onset of high thermal design power
(TDP) processors made by Intel and AMD. 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. For this reason, it is often necessary to supplement thermoelectric cooling devices with a convection-based heatsink or a water-cooling system.
Other cooling methods are forced convection
and phase change cooling which is used in refrigerator
s and can be adapted for computer use. Liquid nitrogen
, liquid helium
, and dry ice
are used as coolants in extreme cases, 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
above 500 GHz, which was done by cooling the chip to 4.5 K (-268.7 °C; -451.6 °F) using liquid helium. These extreme methods are generally impractical in the long term, as they require refilling reservoirs of vaporizing coolant, and condensation
can be formed on chilled components. Moreover, silicon
-based junction gate field-effect transistors (JFET) will degrade below temperatures of roughly 100 K (-173 °C; -280 °F) and eventually cease to function or "freeze out" at 40 K (-233 °C; -388 °F) since the silicon ceases to be semiconducting so using extremely cold coolants may cause devices to fail.
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. A good submersion liquid is Fluorinert
made by 3M
, which is expensive and can only be purchased with a permit. Another option is mineral oil
, but impurities such as those in water might cause it to conduct electricity.
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.
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. 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.
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 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.
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
, Everest
, Superpi, OCCT, IntelBurnTest/Linpack/LinX, SiSoftware Sandra, BOINC, Intel Thermal Analysis Tool and Memtest86
. The hope is that any functional-correctness issues with the overclocked component will show up during these tests, and if no errors are detected during the test, the component is then deemed "stable". Since fault coverage is important in 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".
s 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".
s 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). A widely used test of stability is Prime95 as this has in-built error checking and the computer fails if unstable.
Given only 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
, 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, so a great increase in memory bandwidth may be unnoticeable to a user depending on the applications used. Other benchmarks, such as 3DMark attempt to replicate game conditions.
. 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 fraud
ulent.
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, which offers an attractive solution for enthusiasts seeking an improved performance without sacrificing common warranty protections. Such factory-overclocked products may cost a little more than standard components, but may be more cost-effective than a product with a higher specification.
Naturally, manufacturers would prefer enthusiasts to pay additional money for profitable high-end products, in addition to concerns of less reliable components and shortened product life spans affecting brand image. It is speculated that such concerns are often motivating factors for manufacturers to implement overclocking prevention mechanisms such as CPU locking
. These measures are sometimes marketed as a consumer protection
benefit, which typically generates a negative reception from overclocking enthusiasts.
Another reason for the low default clock speeds is the exponential increase in heat produced. A moderately overclocked chip might produce three or four times as much heat, or more. Expensive cooling solutions are often required in order to achieve higher clock rates.
's Precision, RivaTuner
, ATI
Overdrive (on ATI
cards only), MSI
Afterburner, Zotac Firestorm on Zotac cards, or the PEG Link Mode
on Asus
motherboard
s. Overclocking a GPU will often yield a marked increase in performance in synthetic benchmarks, and usually will improve game performance too.
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 itself, while white, flashing dots appearing randomly (usually in groups) on the screen often mean that the card's RAM 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/clock rate
/voltage limits. If seen at normal clock rate
, voltage and temperature, they may indicate faults with the card itself. However, if the video card is simply clocked too high and doesn't overheat then the artifacts are a bit different. There are many different ways for this to show up and any irregularities should be considered but usually if the core is pushed too hard black circles or blobs appear on the screen and overclocking the video memory beyond its limits usually results in the application or the entire operating system crashing. Luckily though, after the computer is restarted the settings is reset to stock (stored in the video card firmware) and the maximum clock rate
of that specific card has been found.
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. A pencil volt mod refers to changing a resistor's value on the graphics card by drawing across it with a graphite pencil. This results in a change of GPU voltage. It is also worth mentioning that adding physical elements to the video card immediately voids the warranty.
Flashing refers to using the firmware
of another card, based on the same core and design specs, to "override" the original firmware, thus effectively making it a higher model card; however, 'flashing' can be difficult, and sometimes a bad flash can be irreversible. Sometimes stand-alone
software to modify the firmware files can be found, i.e. NiBiTor, (GeForce 6/7 series are well regarded in this aspect). It is not necessary to acquire a firmware file from a better model video card (although it should be said that the card in which firmware is to be used should be compatible, i.e. the same model base, design and/or manufacture process, revisions etc.). For example, video cards with 3D accelerators (the vast majority of today's market) 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 in the middle of 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 also have certain abilities not directly connected with overclocking. For example, Nvidia's GeForce 6600GT
(AGP flavor) features a temperature monitor (used internally by the card), which is invisible to the user in the 'vanilla' version of the card's firmware. Modifying the firmware can allow a 'Temperature' tab to become visible in the card driver's advanced menu.
Unlocking refers to enabling extra pipelines
and/or pixel shaders. The 6800LE
, the 6800GS
and 6800
(AGP
models only), Radeon X800
Pro VIVO 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 GPU
core as a 6800GT
or Ultra, but may not have passed inspection when all their pipelines and shaders were unlocked. In more recent generations, both ATI and Nvidia have laser cut pipelines to prevent this practice..
It is important to remember that while pipeline unlocking sounds very promising, there is absolutely no way of determining if these 'unlocked' pipelines will operate without errors, or at all (this information is solely at the manufacturer's discretion). In a worst-case scenario, the card may not start up ever again, resulting in a 'dead' piece of equipment
. It is possible to revert to the card's previous settings, but it involves manual firmware flashing using special tools and an identical but original firmware chip.
The latest video card series from AMD (Formerly ATI
) as of 2011, the Radeon HD6900
series, can also be unlocked. The Radeon HD6950 (2GB model) can either be flashed with the Radeon HD6970's firmware, or unlocked modifying the original firmware, but using the first method also increases the core and memory speed to those of a Radeon HD6970 (which may not be possible with every card). Only the 2GB model of the Radeon HD6950 can be flashed with the Radeon HD6970's firmware as no HD6970 model, with 1GB of memory, exists.
Although flashing a 6950 to a 6970 may sound like a good idea, it only works on reference models.
Computer hardware
Personal computer hardware are component devices which are typically installed into or peripheral to a computer case to create a personal computer upon which system software is installed including a firmware interface such as a BIOS and an operating system which supports application software that...
at a higher clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
(more clock cycles per second) than it was designed for or was specified by the manufacturer, but some manufacturers purposely underclock their components to improve battery life. Many people just overclock or 'rightclock' their hardware to improve their performance. This is practiced more by enthusiasts than professional users seeking an increase in the performance of their computers, as overclocking carries risks of less reliable functioning and damage. There are several purposes for overclocking: for professional users overclocking allows pushing the boundary of professional personal computing capacity therefore allowing improved productivity or allows testing over-the-horizon technologies beyond that possible with the available component specifications before entering the specialized computing realm and pricing - this leverages the manufacturing practice to specify components to a level that optimizes yield and profit margin, some components are capable of more; there are also hobbyists that, like car enthusiasts, enjoy building, tuning, and comparison racing their systems with standardized benchmark software. Some hobbyists purchase less expensive computer components and overclock to higher clock rates in an attempt to save money but achieve the same performance. A similar but slightly different approach to cost saving is overclocking outdated components to keep pace with new system requirements
System requirements
To be used efficiently, all computer software needs certain hardware components or other software resources to be present on a computer. These pre-requisites are known as system requirements and are often used as a guideline as opposed to an absolute rule. Most software defines two sets of system...
, rather than purchasing new hardware. This approach lowers the cost of a failure since the system is fully depreciated and new system is needed anyways.;
People who overclock their components mainly focus their efforts on processors
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
, video card
Video card
A video card, Graphics Card, or Graphics adapter is an expansion card which generates output images to a display. Most video cards offer various functions such as accelerated rendering of 3D scenes and 2D graphics, MPEG-2/MPEG-4 decoding, TV output, or the ability to connect multiple monitors...
s, motherboard
Motherboard
In personal computers, a motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple...
chipset
Chipset
A chipset, PC chipset, or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product.- Computers :...
s, and RAM
Random-access memory
Random access memory is a form of computer data storage. Today, it takes the form of integrated circuits that allow stored data to be accessed in any order with a worst case performance of constant time. Strictly speaking, modern types of DRAM are therefore not random access, as data is read in...
. It is done through manipulating the CPU multiplier
CPU multiplier
In computing, the clock multiplier measures the ratio of an internal CPU clock rate to the externally supplied clock. A CPU with a 10x multiplier will thus see 10 internal cycles for every external clock cycle...
and the rate of the external clock (such as a front-side bus (FSB) clock) until a maximum stable operating frequency is reached. While the idea is simple, variation in the electrical and physical characteristics of computing systems complicates the process. Power consumption of digital circuits often increases with frequency or clocking speed. The high-frequency operation of semiconductor device
Semiconductor device
Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide, as well as organic semiconductors. Semiconductor devices have replaced thermionic devices in most applications...
s as used in computers to a certain extent improves with an increase in voltage; but operation at high speed and increased voltage increases power dissipation
CPU power dissipation
Central processing unit power dissipation or CPU power dissipation is the process in which central processing units consume electrical energy, and dissipate this energy both by the action of the switching devices contained in the CPU and by the energy lost in the form of heat due to the impedance...
and heating. Overheating caused by higher dissipation, and operation at higher voltage regardless of power, can cause malfunctioning or permanent damage. Increasing voltage supplied and improving cooling can increase the maximum stable operating speed, subject to these risks.
CPU multipliers, bus dividers, voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
s, thermal loads, cooling techniques and several other factors such as individual semiconductor clock and thermal tolerances can affect the performance of the computer.
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 rateClock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
. However, supplying the power with improper settings or applying excessive voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
can permanently damage a component. Since tight tolerances are required for overclocking, only more expensive motherboards have built-in overclocking capabilities. Motherboards with fewer features, such as those found in original equipment manufacturer
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
(OEM) systems, often do not support overclocking.
Cooling
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
produce heat generated by the movement of electrical current. As clock frequencies in digital circuit
Digital circuit
Digital electronics represent signals by discrete bands of analog levels, rather than by a continuous range. All levels within a band represent the same signal state...
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
Thermal Design Power
The thermal design power , sometimes called thermal design point, refers to the maximum amount of power the cooling system in a computer is required to dissipate. For example, a laptop's CPU cooling system may be designed for a 20 watt TDP, which means that it can dissipate up to 20 watts of heat...
(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 will raise power consumption exponentially however, and in turn the amount of power that must be dissipated. 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 MOSFET
MOSFET
The metal–oxide–semiconductor field-effect transistor is a transistor used for amplifying or switching electronic signals. The basic principle of this kind of transistor was first patented by Julius Edgar Lilienfeld in 1925...
device characteristics.
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
Fan (mechanical)
A mechanical fan is a machine used to create flow within a fluid, typically a gas such as air.A fan consists of a rotating arrangement of vanes or blades which act on the air. Usually, it is contained within some form of housing or case. This may direct the airflow or increase safety by preventing...
, larger heat sink
Heat sink
A heat sink is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems and the radiator in a car...
s, heat pipe
Heat pipe
A heat pipe or heat pin is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces....
s 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
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
, which has high thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
, but is expensive. Aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
is more widely used; it has poorer thermal conductivity, but is significantly cheaper than copper. Heat pipe
Heat pipe
A heat pipe or heat pin is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces....
s are commonly used to improve conductivity. Many heatsinks combine two or more materials to achieve a balance between performance and cost.
Water cooling carries waste heat
Waste heat
Waste heat sometimes called Secondary heat or Low-grade heat refers to heat produced by machines, electrical equipment and industrial processes for which no useful application is found. Energy is often produced by a heat engine, running on a source of high-temperature heat...
to a radiator. Thermoelectric cooling
Thermoelectric cooling
Thermoelectric cooling uses the Peltier effect to create a heat flux between the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other side against the...
devices, also known as Peltier devices, are recently popular with the onset of high thermal design power
Thermal Design Power
The thermal design power , sometimes called thermal design point, refers to the maximum amount of power the cooling system in a computer is required to dissipate. For example, a laptop's CPU cooling system may be designed for a 20 watt TDP, which means that it can dissipate up to 20 watts of heat...
(TDP) processors made by Intel and AMD. Thermoelectric cooling devices create temperature differences between two plates by running an electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
through the plates. This method of cooling is highly effective, but itself generates significant heat. For this reason, it is often necessary to supplement thermoelectric cooling devices with a convection-based heatsink or a water-cooling system.
Forced convection
Forced convection is a mechanism, or type of heat transport in which fluid motion is generated by an external source...
and phase change cooling which is used in refrigerator
Refrigerator
A refrigerator is a common household appliance that consists of a thermally insulated compartment and a heat pump that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room...
s and can be adapted for computer use. Liquid nitrogen
Liquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...
, liquid helium
Liquid helium
Helium exists in liquid form only at extremely low temperatures. The boiling point and critical point depend on the isotope of the helium; see the table below for values. The density of liquid helium-4 at its boiling point and 1 atmosphere is approximately 0.125 g/mL Helium-4 was first liquefied...
, and dry ice
Dry ice
Dry ice, sometimes referred to as "Cardice" or as "card ice" , is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue...
are used as coolants in extreme cases, such as record-setting attempts or one-off experiments rather than cooling an everyday system. In June 2006, IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
and Georgia Institute of Technology
Georgia Institute of Technology
The Georgia Institute of Technology is a public research university in Atlanta, Georgia, in the United States...
jointly announced a new record in silicon-based chip clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
above 500 GHz, which was done by cooling the chip to 4.5 K (-268.7 °C; -451.6 °F) using liquid helium. These extreme methods are generally impractical in the long term, as they require refilling reservoirs of vaporizing coolant, and condensation
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
can be formed on chilled components. Moreover, silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
-based junction gate field-effect transistors (JFET) will degrade below temperatures of roughly 100 K (-173 °C; -280 °F) and eventually cease to function or "freeze out" at 40 K (-233 °C; -388 °F) since the silicon ceases to be semiconducting so using extremely cold coolants may cause devices to fail.
Submersion cooling, used by the Cray-2
Cray-2
The Cray-2 was a four-processor ECL vector supercomputer made by Cray Research starting in 1985. It was the fastest machine in the world when it was released, replacing the Cray Research X-MP designed by Steve Chen in that spot...
supercomputer
Supercomputer
A supercomputer is a computer at the frontline of current processing capacity, particularly speed of calculation.Supercomputers are used for highly calculation-intensive tasks such as problems including quantum physics, weather forecasting, climate research, molecular modeling A supercomputer is a...
, 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. A good submersion liquid is Fluorinert
Fluorinert
Fluorinert is the trademarked brand name for the line of electronics coolant liquids sold commercially by 3M. It is an electrically insulating, stable fluorocarbon-based fluid which is used in various cooling applications. It is mainly used for cooling electronics...
made by 3M
3M
3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
, which is expensive and can only be purchased with a permit. Another option is mineral oil
Mineral oil
A mineral oil is any of various colorless, odorless, light mixtures of alkanes in the C15 to C40 range from a non-vegetable source, particularly a distillate of petroleum....
, but impurities such as those in water might cause it to conduct electricity.
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 corruptionReliability, Availability and Serviceability
reliability, availability, and serviceability are computer hardware engineering terms. It originated from IBM to advertise the robustness of their mainframe computers. The concept is often known by the acronym RAS....
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.
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. Achieving good fault coverage
Fault coverage
Fault coverage refers to the percentage of some type of fault that can be detected during the test of any engineered system. High fault coverage is particularly valuable during manufacturing test, and techniques such as Design For Test and automatic test pattern generation are used to increase...
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.
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 flags
Status register
A status register or flag register is a collection of flag bits for a processor. An example is the FLAGS register of the x86 architecture....
; if the flags are not checked, the error will go undetected.
To further complicate matters, in process technologies such as silicon on insulator
Silicon on insulator
Silicon on insulator technology refers to the use of a layered silicon-insulator-silicon substrate in place of conventional silicon substrates in semiconductor manufacturing, especially microelectronics, to reduce parasitic device capacitance and thereby improving performance...
(SOI), devices display hysteresis
Hysteresis
Hysteresis is the dependence of a system not just on its current environment but also on its past. This dependence arises because the system can be in more than one internal state. To predict its future evolution, either its internal state or its history must be known. If a given input alternately...
—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.
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
Prime95
Prime95 is the name of the Microsoft Windows-based software application written by George Woltman that is used by GIMPS, a distributed computing project dedicated to finding new Mersenne prime numbers....
, Everest
Lavalys
Lavalys is a privately held company from Montreal, Canada. This company is the provider of software products popular amongst computer enthusiasts. It's flagship products are EVEREST Ultimate Edition and EVEREST Corporate Edition. These software are designed for everyday use as well as use in...
, Superpi, OCCT, IntelBurnTest/Linpack/LinX, SiSoftware Sandra, BOINC, Intel Thermal Analysis Tool and Memtest86
Memtest86
Memtest86 and Memtest86+ are open source memory test software programs designed to test and stress test an x86 architecture computer's random access memory for errors...
. The hope is that any functional-correctness issues with the overclocked component will show up during these tests, and if no errors are detected during the test, the component is then deemed "stable". Since fault coverage is important in stability testing
Software testing
Software testing is an investigation conducted to provide stakeholders with information about the quality of the product or service under test. Software testing can also provide an objective, independent view of the software to allow the business to appreciate and understand the risks of software...
, 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 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 rateClock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
s are manufactured by the same process, and tested after manufacture to determine their actual ratings. The clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
that the component is rated for is at or below the clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
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
Bob Colwell
Robert P. "Bob" Colwell is an electrical engineer who worked at Intel and is now Deputy Director of the Microsystems Technology Office at DARPA. He was the chief IA-32 architect on the Pentium Pro, Pentium II, Pentium III, and Pentium 4 microprocessors. Bob retired from Intel in 2000...
calls overclocking an "uncontrolled experiment in better-than-worst-case system operation".
Measuring effects of overclocking
BenchmarkBenchmark (computing)
In computing, a benchmark is the act of running a computer program, a set of programs, or other operations, in order to assess the relative performance of an object, normally by running a number of standard tests and trials against it...
s 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). A widely used test of stability is Prime95 as this has in-built error checking and the computer fails if unstable.
Given only 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
Bandwidth (computing)
In computer networking and computer science, bandwidth, network bandwidth, data bandwidth, or digital bandwidth is a measure of available or consumed data communication resources expressed in bits/second or multiples of it .Note that in textbooks on wireless communications, modem data transmission,...
, without taking into consideration how higher clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
s in this aspect will improve the system performance as a whole. Apart from demanding applications such as video encoding, high-demand database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
s and scientific computing, memory bandwidth
Memory bandwidth
Memory bandwidth is the rate at which data can be read from or stored into a semiconductor memory by a processor. Memory bandwidth is usually expressed in units of bytes/second, though this can vary for systems with natural data sizes that are not a multiple of the commonly used 8-bit bytes.Memory...
is typically not a bottleneck, so a great increase in memory bandwidth may be unnoticeable to a user depending on the applications used. Other benchmarks, such as 3DMark attempt to replicate game conditions.
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 rateClock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
. In some cases an overclocked component is functionally identical to a non-overclocked one of the new clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
, 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 fraud
Fraud
In criminal law, a fraud is an intentional deception made for personal gain or to damage another individual; the related adjective is fraudulent. The specific legal definition varies by legal jurisdiction. Fraud is a crime, and also a civil law violation...
ulent.
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, which offers an attractive solution for enthusiasts seeking an improved performance without sacrificing common warranty protections. Such factory-overclocked products may cost a little more than standard components, but may be more cost-effective than a product with a higher specification.
Naturally, manufacturers would prefer enthusiasts to pay additional money for profitable high-end products, in addition to concerns of less reliable components and shortened product life spans affecting brand image. It is speculated that such concerns are often motivating factors for manufacturers to implement overclocking prevention mechanisms such as CPU locking
CPU locking
CPU locking is the process of permanently setting a 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 models are very resistant to unlocking to prevent overclocking by users...
. These measures are sometimes marketed as a consumer protection
Consumer protection
Consumer protection laws designed to ensure fair trade competition and the free flow of truthful information in the marketplace. The laws are designed to prevent businesses that engage in fraud or specified unfair practices from gaining an advantage over competitors and may provide additional...
benefit, which typically generates a negative reception from overclocking enthusiasts.
Another reason for the low default clock speeds is the exponential increase in heat produced. A moderately overclocked chip might produce three or four times as much heat, or more. Expensive cooling solutions are often required in order to achieve higher clock rates.
Advantages
- The user can, in many cases, purchase a lower performance, cheaper component and overclock it to the clock rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
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 motherboardMotherboardIn personal computers, a motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple...
s with AMD Athlon 64Athlon 64The Athlon 64 is an eighth-generation, AMD64-architecture microprocessor produced by AMD, released on September 23, 2003. It is the third processor to bear the name Athlon, and the immediate successor to the Athlon XP...
processors limit the clock rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
of four units of RAM to 333 MHzHertzThe hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
. However, the memory performance is computed by dividing the processor clock rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
(which is a base number times a CPU multiplierCPU multiplierIn computing, the clock multiplier measures the ratio of an internal CPU clock rate to the externally supplied clock. A CPU with a 10x multiplier will thus see 10 internal cycles for every external clock cycle...
, for instance 1.8 GHz is most likely 9×200 MHz) by a fixed integerIntegerThe integers are formed by the natural numbers together with the negatives of the non-zero natural numbers .They are known as Positive and Negative Integers respectively...
such that, at a stock clock rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
, the RAM would run at a clock rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
near 333 MHz. Manipulating elements of how the processor clock rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
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 rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
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 PCMarkPCMarkPCMark is a computer benchmark tool developed by Futuremark to test the performance of a PC at the system and component level. In most cases the tests in PCMark are designed to represent typical home user workloads. Running PCMark produces a score with higher numbers indicating better performance...
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 rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
s and/or voltages result in higher power consumption. - While overclocked systems may be tested for stability before use using programs that "burn" the computer, these programs create an artificial strain that pushes individual or many components to their maximum (or beyond it). Some common stability programs are Prime95Prime95Prime95 is the name of the Microsoft Windows-based software application written by George Woltman that is used by GIMPS, a distributed computing project dedicated to finding new Mersenne prime numbers....
, Super PI (32M), Intel TAT, LinX, PCMark, FurMark and OCCT. 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, WindowsMicrosoft WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
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. Microsoft says this of errors in upgrading to Windows XP: "Your computer [may be] over-clocked. Because installing Windows is very memory-intensive, decoding errors may occur when files are extracted from the 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"). Most warranties do not cover damage caused by overclocking. Some motherboards offer safety measures that will stop this from happening (e.g. limitations on FSB increase) so that only voltage control alterations can cause such harm.
- Some motherboards are designed to use the airflow from a standard CPU fan in order to cool other heatsinks, such as the northbridge. If the CPU heatsink is changed on such boards, other heatsinks may receive insufficient cooling.
- Overclocking a PC component may void its warranty (depending on the conditions of sale).
- Changing the Heatsink on a Graphics Card often voids its warranty.
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 quadratically. 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 lossData lossData loss is an error condition in information systems in which information is destroyed by failures or neglect in storage, transmission, or processing. Information systems implement backup and disaster recovery equipment and processes to prevent data loss or restore lost data.Data loss is...
. 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 liquidWatercoolingWater cooling is a method of heat removal from components and industrial equipment. As opposed to air cooling, water is used as the heat conductor. Water cooling is commonly used for cooling automobile internal combustion engines and large industrial facilities such as steam electric power plants,...
cooling may result in failure of the cooling system, which may result in water damageWater damageWater damage describes a large number of possible losses caused by water intruding where it will enable attack of a material or system by destructive processes such as rotting of wood, growth, rusting of steel, de-laminating of materials such as plywood , and many, many others.The damage may be...
. - With sub-zero cooling methods such as phase-change cooling or liquid nitrogenLiquid nitrogenLiquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...
, extra precautions such as foam or spray insulation must be made to prevent water from condensing upon the PCB and other areas. This can cause the board to become "frosted" or covered in frost. While the water is frozen it is usually safe, however once it melts it can cause shorts and other malignant issues. - 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 heat sinkHeat sinkA heat sink is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems and the radiator in a car...
s designed for chips (or components) which do not generate enough heat to benefit from these devices (capacitors, for example).
Limitations
The utility of overclocking is limited for a few reasons:- Personal computerPersonal computerA personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
s 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 InternetInternetThe Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
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 processingWord processorA word processor is a computer application used for the production of any sort of printable material....
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 rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
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 secondFrame rateFrame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
(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 usually bound by the GPUGraphics processing unitA graphics processing unit or GPU is a specialized circuit designed to rapidly manipulate and alter memory in such a way so as to accelerate the building of images in a frame buffer intended for output to a display...
at resolutions beyond 1024×768 . One exception to this rule is when the overclocked component is the bottleneck of the system, in which case the most gains can be seen. - Computational workloads which require absolute mathematical accuracy such as spreadsheets and banking applications benefit significantly from deterministic and correct processor operation.
Graphics cards
Graphics cards can also be overclocked, with utilities such as EVGAEVGA Corporation
EVGA Corporation is a company that produces NVIDIA based consumer computer hardware, as well as Intel based motherboards. Founded in July 1999, its current headquarters is in Brea, California.- Products :...
's Precision, RivaTuner
RivaTuner
RivaTuner is a freeware program developed by Alexey Nicolaychuk for the NVIDIA video cards, from the Riva TNT to the GeForce 200 Series, which also has limited support for the ATI video cards from the Radeon 8500 and above....
, ATI
ATI Technologies
ATI Technologies Inc. was a semiconductor technology corporation based in Markham, Ontario, Canada, that specialized in the development of graphics processing units and chipsets. Founded in 1985 as Array Technologies Inc., the company was listed publicly in 1993 and was acquired by Advanced Micro...
Overdrive (on ATI
ATI Technologies
ATI Technologies Inc. was a semiconductor technology corporation based in Markham, Ontario, Canada, that specialized in the development of graphics processing units and chipsets. Founded in 1985 as Array Technologies Inc., the company was listed publicly in 1993 and was acquired by Advanced Micro...
cards only), MSI
Micro-Star International
Micro-Star International Co., Ltd is a Taiwan-based electronics company and one of the world's largest motherboard and video card manufacturers.-Overview:MSI is one of the top three motherboard and video card manufacturers worldwide...
Afterburner, Zotac Firestorm on Zotac cards, or the PEG Link Mode
PEG Link Mode
PEG Link Mode is a feature available in the BIOS of some ASUS motherboards, which automatically overclocks the video card by a small amount. The possible settings for the option are Auto, Slow , Normal , Fast, and Faster...
on Asus
ASUS
ASUSTeK Computer Incorporated is a multinational computer technology and consumer electronics product manufacturer headquartered in Taipei, Taiwan. Its product range includes motherboards, desktops, laptops, monitors, tablet PCs, servers and mobile phones...
motherboard
Motherboard
In personal computers, a motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, providing connectors for other peripherals. The motherboard is sometimes alternatively known as the mainboard, system board, or, on Apple...
s. Overclocking a GPU will often yield a marked increase in performance in synthetic benchmarks, and usually will improve game performance too.
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 itself, while white, flashing dots appearing randomly (usually in groups) on the screen often mean that the card's RAM 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/clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
/voltage limits. If seen at normal clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
, voltage and temperature, they may indicate faults with the card itself. However, if the video card is simply clocked too high and doesn't overheat then the artifacts are a bit different. There are many different ways for this to show up and any irregularities should be considered but usually if the core is pushed too hard black circles or blobs appear on the screen and overclocking the video memory beyond its limits usually results in the application or the entire operating system crashing. Luckily though, after the computer is restarted the settings is reset to stock (stored in the video card firmware) and the maximum clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
of that specific card has been found.
Some overclockers use a hardware voltage modification where a potentiometer
Potentiometer
A potentiometer , informally, a pot, is a three-terminal resistor with a sliding contact that forms an adjustable voltage divider. If only two terminals are used , it acts as a variable resistor or rheostat. Potentiometers are commonly used to control electrical devices such as volume controls on...
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. A pencil volt mod refers to changing a resistor's value on the graphics card by drawing across it with a graphite pencil. This results in a change of GPU voltage. It is also worth mentioning that adding physical elements to the video card immediately voids the warranty.
Alternatives
Flashing and Unlocking are two popular ways to gain performance out of a video card, without technically overclocking.Flashing refers to using the firmware
Firmware
In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...
of another card, based on the same core and design specs, to "override" the original firmware, thus effectively making it a higher model card; however, 'flashing' can be difficult, and sometimes a bad flash can be irreversible. Sometimes stand-alone
Stand-alone
Standalone software can mean:* Computer software that can work offline, i.e. does not necessarily require network connection to function* Software that is not a part of some software bundle...
software to modify the firmware files can be found, i.e. NiBiTor, (GeForce 6/7 series are well regarded in this aspect). It is not necessary to acquire a firmware file from a better model video card (although it should be said that the card in which firmware is to be used should be compatible, i.e. the same model base, design and/or manufacture process, revisions etc.). For example, video cards with 3D accelerators (the vast majority of today's market) have two voltage and clock rate
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
settings - one for 2D and one for 3D - but were designed to operate with three voltage stages, the third being somewhere in the middle of 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
Clock rate
The clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
, 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 also have certain abilities not directly connected with overclocking. For example, Nvidia's GeForce 6600GT
GeForce
GeForce is a brand of graphics processing units designed by Nvidia. , there have been eleven iterations of the design. The first GeForce products were discrete GPUs designed for use on add-on graphics boards, intended for the high-margin PC gaming market...
(AGP flavor) features a temperature monitor (used internally by the card), which is invisible to the user in the 'vanilla' version of the card's firmware. Modifying the firmware can allow a 'Temperature' tab to become visible in the card driver's advanced menu.
Unlocking refers to enabling extra pipelines
Graphics pipeline
In 3D computer graphics, the terms graphics pipeline or rendering pipeline most commonly refers to the current state of the art method of rasterization-based rendering as supported by commodity graphics hardware. The graphics pipeline typically accepts some representation of a three-dimensional...
and/or pixel shaders. The 6800LE
GeForce 6 Series
The GeForce 6 Series is Nvidia's sixth generation of GeForce graphic processing units. Launched on April 14, 2004, the GeForce 6 family introduced PureVideo post-processing for video, SLI technology, and Shader Model 3.0 support .-GeForce 6 Series features:-SLI:The Scalable Link...
, the 6800GS
GeForce 6 Series
The GeForce 6 Series is Nvidia's sixth generation of GeForce graphic processing units. Launched on April 14, 2004, the GeForce 6 family introduced PureVideo post-processing for video, SLI technology, and Shader Model 3.0 support .-GeForce 6 Series features:-SLI:The Scalable Link...
and 6800
GeForce 6 Series
The GeForce 6 Series is Nvidia's sixth generation of GeForce graphic processing units. Launched on April 14, 2004, the GeForce 6 family introduced PureVideo post-processing for video, SLI technology, and Shader Model 3.0 support .-GeForce 6 Series features:-SLI:The Scalable Link...
(AGP
Accelerated Graphics Port
The Accelerated Graphics Port is a high-speed point-to-point channel for attaching a video card to a computer's motherboard, primarily to assist in the acceleration of 3D computer graphics. Since 2004 AGP has been progressively phased out in favor of PCI Express...
models only), Radeon X800
Radeon R420
The Radeon R420 core from ATI Technologies was the company's basis for its 3rd-generation DirectX 9.0/OpenGL 2.0-capable graphics cards. Used first on the Radeon X800, R420 was produced on a 0.13 micrometer low-K process and used GDDR-3 memory...
Pro VIVO 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 GPU
Graphics processing unit
A graphics processing unit or GPU is a specialized circuit designed to rapidly manipulate and alter memory in such a way so as to accelerate the building of images in a frame buffer intended for output to a display...
core as a 6800GT
GeForce 6 Series
The GeForce 6 Series is Nvidia's sixth generation of GeForce graphic processing units. Launched on April 14, 2004, the GeForce 6 family introduced PureVideo post-processing for video, SLI technology, and Shader Model 3.0 support .-GeForce 6 Series features:-SLI:The Scalable Link...
or Ultra, but may not have passed inspection when all their pipelines and shaders were unlocked. In more recent generations, both ATI and Nvidia have laser cut pipelines to prevent this practice..
It is important to remember that while pipeline unlocking sounds very promising, there is absolutely no way of determining if these 'unlocked' pipelines will operate without errors, or at all (this information is solely at the manufacturer's discretion). In a worst-case scenario, the card may not start up ever again, resulting in a 'dead' piece of equipment
Brick (electronics)
When used in reference to consumer electronics, "brick" describes a device that cannot function in any capacity . This usage derives from the fact that some electronic devices are vaguely brick-shaped, and so those which do not function are useful only as actual bricks. The term can also be used...
. It is possible to revert to the card's previous settings, but it involves manual firmware flashing using special tools and an identical but original firmware chip.
The latest video card series from AMD (Formerly ATI
Ati
As a word, Ati may refer to:* Ati, a town in Chad* Ati, a Negrito ethnic group in the Philippines* Ati-Atihan Festival, an annual celebration held in the Philippines* Ati, a queen of the fabled Land of Punt in Africa...
) as of 2011, the Radeon HD6900
Northern Islands (GPU family)
The Northern Islands series is a family of GPUs developed by Advanced Micro Devices for its Radeon line, based on the 40 nm process.Starting with this family, the former ATI brand was officially discontinued in favor of making a correlation between the graphics products and the AMD branding for...
series, can also be unlocked. The Radeon HD6950 (2GB model) can either be flashed with the Radeon HD6970's firmware, or unlocked modifying the original firmware, but using the first method also increases the core and memory speed to those of a Radeon HD6970 (which may not be possible with every card). Only the 2GB model of the Radeon HD6950 can be flashed with the Radeon HD6970's firmware as no HD6970 model, with 1GB of memory, exists.
Although flashing a 6950 to a 6970 may sound like a good idea, it only works on reference models.
See also
- Clock rateClock rateThe clock rate typically refers to the frequency that a CPU is running at.For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave...
- CPU lockingCPU lockingCPU locking is the process of permanently setting a 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 models are very resistant to unlocking to prevent overclocking by users...
- CPU-ZCPU-ZCPU-Z is a freeware system profiler application for Microsoft Windows that detects the central processing unit, RAM, motherboard chipset, and other hardware features of a modern personal computer, and presents the information in one window.CPU-Z is more in-depth in almost all areas than the tools...
- Dynamic voltage scalingDynamic voltage scalingDynamic 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...
- Fake bootFake bootFake boot is a feature of the BIOS and may occur after changes to the BIOS. Changing some parameters in the BIOS will cause this issue, even for just setting a system as stock speeds, such as initializing the current CPU and memory clocks...
- Serial Presence DetectSerial Presence DetectSerial presence detect refers to a standardized way to automatically access information about a computer memory module. Earlier 72-pin SIMMs included 5 pins which provided 5 bits of parallel presence detect data, but the 168-pin DIMM standard changed to a serial presence detect to encode much...
(SPD), memory hardware feature to auto-configure timings - Super PI
- UnderclockingUnderclockingUnderclocking, also known as downclocking, is the practice of modifying a synchronous circuit's timing settings to run at a lower clock rate than it was specified to operate at. It may be said to be the computer equivalent of driving a car below the speed limit...
- UNIVAC I Overdrive, 1952 unofficial modificationUNIVAC IThe UNIVAC I was the first commercial computer produced in the United States. It was designed principally by J. Presper Eckert and John Mauchly, the inventors of the ENIAC...
External links
- How to Overclock CPUs and RAM by Vito Cassisi
- OverClocked inside
- How to Overclock a PC, WikiHow
- How to Overclock Intel CPUs, Tom's Tech Reviews
- Overclocking Software tips and Review, CPU Overclocking Software