ravanfar
یک شنبه 29 اردیبهشت 1387, 09:33 صبح
بعد از دو ماه از شروع به کار وب سایت Overclocking.ir و خبر از برگزاری اولین فستیوال اورکلاکینگ ایران و هم زمان ثبت نام از علاقه مندان به شرکت در آن، بالاخره این فستیوال در روزهای پنج شنبه و جمعه، 26 و 27 اردیبهشت ماه با شرکت بیش از ششصد نفر از علاقه مندان به اورکلاکینگ برگزار گردید.
لینک:
http://www.overclocking.ir/homepage.htm
توضیحات:
بنقل از wikipedia:
Overclocking
From Wikipedia, the free encyclopedia
• Ten things you may not know about Wikipedia (http://en.wikipedia.org/wiki/Wikipedia:Ten_things_you_may_not_know_about_Wikipe dia) •
Jump to: navigation (http://en.wikipedia.org/wiki/Overclocking#column-one), search (http://en.wikipedia.org/wiki/Overclocking#searchInput)
"Overclocked" redirects here. For the website, see OverClocked ReMix (http://en.wikipedia.org/wiki/OverClocked_ReMix). For the book, see Overclocked: Stories of the Future Present (http://en.wikipedia.org/wiki/Overclocked:_Stories_of_the_Future_Present).
http://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Overclock.jpg/350px-Overclock.jpg (http://en.wikipedia.org/wiki/Image:Overclock.jpg) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:Overclock.jpg)
AMD Athlon XP (http://en.wikipedia.org/wiki/Athlon_XP) Overclocking BIOS (http://en.wikipedia.org/wiki/BIOS) Setup on ABIT NF7-S. Front side bus (http://en.wikipedia.org/wiki/Front_side_bus) frequency (External clock) has increased from 133 MHz (http://en.wikipedia.org/wiki/MHz) to 148 MHz, and clock multiplier (http://en.wikipedia.org/wiki/Clock_multiplier) factor has changed from 13.5 to 16.5.
Overclocking is the process of forcing a computer component (http://en.wikipedia.org/wiki/Computer_hardware) to run at a higher clock rate (http://en.wikipedia.org/wiki/Clock_rate) than it was designed for or was designated by the manufacturer, usually practiced by personal computer (http://en.wikipedia.org/wiki/Personal_computer) enthusiasts in order to increase the performance of their computers. Some of them purchase low-end computer components which they then overclock to higher speeds, or overclock high-end components to attain levels of performance beyond the default factory settings. Others overclock outdated components to keep pace with new system requirements (http://en.wikipedia.org/wiki/System_requirements), rather than purchasing new hardware products as expected by the computer industry (http://en.wikipedia.org/wiki/Computer_industry).[1] (http://en.wikipedia.org/wiki/Overclocking#cite_note-0)
Users who overclock their components mainly focus their efforts on processors (http://en.wikipedia.org/wiki/Central_processing_unit), video cards (http://en.wikipedia.org/wiki/Video_card), motherboard (http://en.wikipedia.org/wiki/Motherboard) chipsets (http://en.wikipedia.org/wiki/Chipset), and Random Access Memory (RAM) (http://en.wikipedia.org/wiki/Random_Access_Memory). It is done through manipulating the CPU multiplier (http://en.wikipedia.org/wiki/CPU_multiplier) and the motherboard's front side bus (http://en.wikipedia.org/wiki/Front_side_bus) (FSB) speed 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. CPU multipliers, bus dividers, voltages (http://en.wikipedia.org/wiki/Voltage), thermal loads, cooling techniques and several other factors can affect it.[2] (http://en.wikipedia.org/wiki/Overclocking#cite_note-1)
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=1)] Considerations
There are several considerations when overclocking. The first consideration is to ensure that it is supplied with adequate power to operate at the new speed. However, supplying the power with improper settings or applying excessive voltage (http://en.wikipedia.org/wiki/Voltage) can permanently damage a component. Since tight tolerances are required for overclocking, only more expensive motherboards—with advanced settings that computer enthusiasts are likely to use—have built-in overclocking capabilities. Motherboards with fewer settings, such as those found in Original Equipment Manufacturer (http://en.wikipedia.org/wiki/Original_Equipment_Manufacturer) (OEM) systems, lack such features in order to eliminate the possibility of misconfiguration and cut down on the support costs and warranty claims to the manufacturer.
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=2)] Cooling
Main article: Computer cooling (http://en.wikipedia.org/wiki/Computer_cooling)
http://upload.wikimedia.org/wikipedia/en/thumb/4/47/Copper_heat_sink_with_pipes.jpg/180px-Copper_heat_sink_with_pipes.jpg (http://en.wikipedia.org/wiki/Image:Copper_heat_sink_with_pipes.jpg) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:Copper_heat_sink_with_pipes.jpg)
High quality heatsinks (http://en.wikipedia.org/wiki/Heatsink) are often made of copper (http://en.wikipedia.org/wiki/Copper).
All electronic circuits (http://en.wikipedia.org/wiki/Electrical_network) produce heat generated by the movement of electrons (http://en.wikipedia.org/wiki/Electron). As clock frequencies in digital circuits (http://en.wikipedia.org/wiki/Digital_circuit) increase, the heat generated by over clocked components also increases. Due to increased heat produced by overclocked components, an effective cooling system is necessary to avoid damaging the hardware. In addition, digital circuits slow down at high temperatures due to changes in metal–oxide–semiconductor field-effect transistor (http://en.wikipedia.org/wiki/MOSFET) (MOSFET) device characteristics. Wire resistance also increases slightly at higher temperatures, contributing to decreased circuit performance.
Because most stock cooling systems are designed for the amount of power produced during non-overclocked use, overclockers typically turn to more effective cooling solutions, such as powerful fans (http://en.wikipedia.org/wiki/Fan_%28mechanical%29) or heavy duty heatsinks (http://en.wikipedia.org/wiki/Heatsinks). Size, shape, and material all influence the ability of a heatsink to dissipate heat. Efficient heatsinks are often made entirely of copper (http://en.wikipedia.org/wiki/Copper), which has a high thermal conductivity (http://en.wikipedia.org/wiki/Thermal_conductivity) but is expensive.[3] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner38-2) Aluminium (http://en.wikipedia.org/wiki/Aluminium) is more widely used; it has poorer thermal conductivity, but is significantly cheaper than copper. Iron (http://en.wikipedia.org/wiki/Iron) and steel (http://en.wikipedia.org/wiki/Steel) are not often used in heatsinks due to their poor thermal conductivity. Silver (http://en.wikipedia.org/wiki/Silver) is used in some designs, its thermal conductivity is higher than copper but it is prohibitively expensive for most applications.[citation needed (http://en.wikipedia.org/wiki/Wikipedia:Citation_needed)] Many heatsinks combine two or more materials to achieve a balance between performance and cost.[3] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner38-2)
http://upload.wikimedia.org/wikipedia/en/thumb/7/7b/DIY_watercooling_T-Line.JPG/180px-DIY_watercooling_T-Line.JPG (http://en.wikipedia.org/wiki/Image:DIY_watercooling_T-Line.JPG) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:DIY_watercooling_T-Line.JPG)
Interior of a water cooled computer, showing CPU water block (http://en.wikipedia.org/wiki/Water_block), tubing and pump
Water cooling (http://en.wikipedia.org/wiki/Water_cooling) and passive liquid coolant (http://en.wikipedia.org/wiki/Coolant) carrying waste heat (http://en.wikipedia.org/wiki/Waste_heat) to a radiator, which is similar to an automobile engine (http://en.wikipedia.org/wiki/Automobile_engine)'s cooling system, provide more effective cooling than heatsink and fan combinations when properly implemented, because liquid is denser than air and therefore offers greater thermal transformation.
Thermoelectric cooling (http://en.wikipedia.org/wiki/Thermoelectric_cooling) devices, also known as Peltier devices, are recently popular with the onset of high Thermal Design Power (http://en.wikipedia.org/wiki/Thermal_Design_Power) (TDP) processors made by Intel and AMD. Thermoelectric cooling devices create temperature differences between two plates by running an electric current (http://en.wikipedia.org/wiki/Electric_current) through the plates. This method of cooling is highly effective but has a drawback that it leads to a lot of excess heat. For this reason, it is often necessary to supplement thermoelectric cooling devices with a convection-based heatsink or a water cooling system.
http://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/2007TaipeiITMonth_IntelOCLiveTest_Overclocking-6.jpg/180px-2007TaipeiITMonth_IntelOCLiveTest_Overclocking-6.jpg (http://en.wikipedia.org/wiki/Image:2007TaipeiITMonth_IntelOCLiveTest_Overclocki ng-6.jpg) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:2007TaipeiITMonth_IntelOCLiveTest_Overclocki ng-6.jpg)
Liquid nitrogen (http://en.wikipedia.org/wiki/Liquid_nitrogen) may be used for cooling an overclocked system, when an extreme measure is needed.
Other cooling methods are forced convection (http://en.wikipedia.org/wiki/Forced_convection) and phase change (http://en.wikipedia.org/wiki/Phase_change) cooling which is used in refrigerators (http://en.wikipedia.org/wiki/Refrigerator). Liquid nitrogen (http://en.wikipedia.org/wiki/Liquid_nitrogen) and dry ice (http://en.wikipedia.org/wiki/Dry_ice) are used as coolants in extreme measures,[4] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner44-3) such as record-setting attempts or one-off experiments rather than cooling an everyday system. These extreme methods are generally impractical in the long term, as they require refilling reservoirs of vaporizing coolant and condensation (http://en.wikipedia.org/wiki/Condensation) is formed on components due to difference between component temperature and air temperature.[4] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner44-3) Moreover, silicon (http://en.wikipedia.org/wiki/Silicon)-based junction gate field-effect transistors (http://en.wikipedia.org/wiki/Junction_gate_field-effect_transistor) (JFET) will degrade below temperatures of roughly 100 K (http://en.wikipedia.org/wiki/Kelvin) (−173 °C (http://en.wikipedia.org/wiki/Celsius)/−280 °F (http://en.wikipedia.org/wiki/Fahrenheit)) and eventually cease to function or "freeze out" at 40 K (−233 °C/−388 °F),[5] (http://en.wikipedia.org/wiki/Overclocking#cite_note-4) so using extremely cold coolants may cause devices to fail.
Submersion cooling, used for Cray-2 (http://en.wikipedia.org/wiki/Cray-2) supercomputer (http://en.wikipedia.org/wiki/Supercomputer), involves sinking a part of computer system directly into a chilled liquid substance that is thermally conductive but sufficiently low in electrical conductivity (http://en.wikipedia.org/wiki/Electrical_conductivity). The advantage of this technique is that no condensation can form on components.[6] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner48-5) A good submersion liquid is Fluorinert (http://en.wikipedia.org/wiki/Fluorinert) made by 3M (http://en.wikipedia.org/wiki/3M), which is expensive and requires permits to purchase it.[6] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner48-5) Another option is mineral oil (http://en.wikipedia.org/wiki/Mineral_oil), but any impurities like water or scenting agents might cause it to conduct electricity.[6] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner48-5)
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=3)] Stability and functional correctness
See also: Stress testing#hardware (http://en.wikipedia.org/wiki/Stress_testing#hardware)
As an overclocked component operates outside of the manufacturer's recommended operating conditions, it may function incorrectly, leading to system instability. An unstable overclocked system, while it may work fast, can be frustrating to use. Another risk is silent data corruption (http://en.wikipedia.org/wiki/Reliability%2C_Availability_and_Serviceability)— errors that are initially undetected. 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 anyone (even the processor manufacturer) to thoroughly test the functionality of a processor. 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 (http://en.wikipedia.org/wiki/Status_register); if the flags are not checked, the error will go undetected. Achieving good fault coverage (http://en.wikipedia.org/wiki/Fault_coverage) requires immense engineering effort, and despite all the resources dedicated to validation by manufacturers, mistakes can still be made. To further complicate matters, in process technologies such as silicon on insulator (http://en.wikipedia.org/wiki/Silicon_on_insulator), devices display hysteresis (http://en.wikipedia.org/wiki/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 speeds 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.[7] (http://en.wikipedia.org/wiki/Overclocking#cite_note-6)
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 a processor-intensive application for testing processors). Popular stress tests include Prime95 (http://en.wikipedia.org/wiki/Prime95), Super PI (http://en.wikipedia.org/wiki/Super_PI), SiSoftware Sandra (http://en.wikipedia.org/w/index.php?title=SiSoftware_Sandra&action=edit&redlink=1), BOINC (http://en.wikipedia.org/wiki/BOINC), Intel Thermal Analysis Tool and Memtest86 (http://en.wikipedia.org/wiki/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 (http://en.wikipedia.org/wiki/Software_testing), the tests are often run for long periods of time, hours or even days.
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=4)] Factors allowing overclocking
http://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Pentium-Dual-Core-E2140-100%25-overclock-2.PNG/180px-Pentium-Dual-Core-E2140-100%25-overclock-2.PNG (http://en.wikipedia.org/wiki/Image:Pentium-Dual-Core-E2140-100%25-overclock-2.PNG) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:Pentium-Dual-Core-E2140-100%25-overclock-2.PNG)
CPU-Z (http://en.wikipedia.org/wiki/CPU-Z) screenshot demonstrating a 100% overclock of the E2140 (http://en.wikipedia.org/wiki/Intel_Pentium_Dual-Core)
Overclockability arises in part due to the economics of the manufacturing processes of CPUs. In most cases, CPUs with different rated clock speeds are manufactured via exactly the same process. The clock speed that the CPU is rated for is at or below the speed 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 have an excess of similarly high-performing parts and cannot sell them all at the flagship price, so some are marked as medium-speed chips to be sold for medium prices. The performance of a given CPU stepping (http://en.wikipedia.org/wiki/Stepping_%28version_numbers%29) usually does not vary as widely as the marketing clock levels[citation needed (http://en.wikipedia.org/wiki/Wikipedia:Citation_needed)].
When a manufacturer rates a chip for a certain speed, it must ensure that the chip functions properly at that speed over the entire range of allowed operating conditions. When overclocking a system, the operating conditions are usually tightly controlled, making the manufacturer's margin available as free headroom. Other system components are generally designed with margins for similar reasons; overclocked systems absorb this designed headroom and operate at lower tolerances. Pentium architect Bob Colwell (http://en.wikipedia.org/wiki/Bob_Colwell) calls overclocking an "uncontrolled experiment in better-than-worst-case system operation".[8] (http://en.wikipedia.org/wiki/Overclocking#cite_note-7)
Some of what appears to be spare margin is actually required for proper operation of a processor throughout its lifetime. As semiconductor devices (http://en.wikipedia.org/wiki/Semiconductor_device) age, various effects such as hot carrier injection (http://en.wikipedia.org/wiki/Hot_carrier_injection), negative bias thermal instability (http://en.wikipedia.org/w/index.php?title=Negative_bias_thermal_instability&action=edit&redlink=1) and electromigration (http://en.wikipedia.org/wiki/Electromigration) reduce circuit performance. When overclocking a new chip it is possible to take advantage of this margin, but as the chip ages this can result in situations where a processor that has operated correctly at overclocked speeds for years spontaneously fails to operate at those same speeds later. If the overclocker is not actively testing for system stability when these effects become significant, errors encountered are likely to be blamed on sources other than the overclocking.
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=5)] Measuring effects of overclocking
Benchmarks (http://en.wikipedia.org/wiki/Benchmark_%28computing%29) 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).
Given only benchmark scores it may be difficult to judge the difference overclocking makes to the computing experience. For example, some benchmarks test only one aspect of the system, such as memory bandwidth (http://en.wikipedia.org/wiki/Bandwidth), without taking into consideration how higher speeds in this aspect will improve the system performance as a whole. Apart from demanding applications such as video encoding, high-demand databases (http://en.wikipedia.org/wiki/Database) and scientific computing (http://en.wikipedia.org/wiki/Scientific_computing), memory bandwidth (http://en.wikipedia.org/wiki/Memory_bandwidth) is typically not a bottleneck (http://en.wikipedia.org/wiki/Bottleneck_%28engineering%29), so a great increase in memory bandwidth may be unnoticeable to a user depending on the applications they prefer to use. Other benchmarks, such as 3DMark (http://en.wikipedia.org/wiki/3D_Mark) attempt to replicate game conditions, but because some tests involve non-deterministic (http://en.wikipedia.org/wiki/Deterministic) physics, such as ragdoll motion, the scene is slightly different each time and small differences in test score are overcome by the noise floor (http://en.wikipedia.org/wiki/Noise_floor).[citation needed (http://en.wikipedia.org/wiki/Wikipedia:Citation_needed)]
....
لینک:
http://www.overclocking.ir/homepage.htm
توضیحات:
بنقل از wikipedia:
Overclocking
From Wikipedia, the free encyclopedia
• Ten things you may not know about Wikipedia (http://en.wikipedia.org/wiki/Wikipedia:Ten_things_you_may_not_know_about_Wikipe dia) •
Jump to: navigation (http://en.wikipedia.org/wiki/Overclocking#column-one), search (http://en.wikipedia.org/wiki/Overclocking#searchInput)
"Overclocked" redirects here. For the website, see OverClocked ReMix (http://en.wikipedia.org/wiki/OverClocked_ReMix). For the book, see Overclocked: Stories of the Future Present (http://en.wikipedia.org/wiki/Overclocked:_Stories_of_the_Future_Present).
http://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Overclock.jpg/350px-Overclock.jpg (http://en.wikipedia.org/wiki/Image:Overclock.jpg) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:Overclock.jpg)
AMD Athlon XP (http://en.wikipedia.org/wiki/Athlon_XP) Overclocking BIOS (http://en.wikipedia.org/wiki/BIOS) Setup on ABIT NF7-S. Front side bus (http://en.wikipedia.org/wiki/Front_side_bus) frequency (External clock) has increased from 133 MHz (http://en.wikipedia.org/wiki/MHz) to 148 MHz, and clock multiplier (http://en.wikipedia.org/wiki/Clock_multiplier) factor has changed from 13.5 to 16.5.
Overclocking is the process of forcing a computer component (http://en.wikipedia.org/wiki/Computer_hardware) to run at a higher clock rate (http://en.wikipedia.org/wiki/Clock_rate) than it was designed for or was designated by the manufacturer, usually practiced by personal computer (http://en.wikipedia.org/wiki/Personal_computer) enthusiasts in order to increase the performance of their computers. Some of them purchase low-end computer components which they then overclock to higher speeds, or overclock high-end components to attain levels of performance beyond the default factory settings. Others overclock outdated components to keep pace with new system requirements (http://en.wikipedia.org/wiki/System_requirements), rather than purchasing new hardware products as expected by the computer industry (http://en.wikipedia.org/wiki/Computer_industry).[1] (http://en.wikipedia.org/wiki/Overclocking#cite_note-0)
Users who overclock their components mainly focus their efforts on processors (http://en.wikipedia.org/wiki/Central_processing_unit), video cards (http://en.wikipedia.org/wiki/Video_card), motherboard (http://en.wikipedia.org/wiki/Motherboard) chipsets (http://en.wikipedia.org/wiki/Chipset), and Random Access Memory (RAM) (http://en.wikipedia.org/wiki/Random_Access_Memory). It is done through manipulating the CPU multiplier (http://en.wikipedia.org/wiki/CPU_multiplier) and the motherboard's front side bus (http://en.wikipedia.org/wiki/Front_side_bus) (FSB) speed 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. CPU multipliers, bus dividers, voltages (http://en.wikipedia.org/wiki/Voltage), thermal loads, cooling techniques and several other factors can affect it.[2] (http://en.wikipedia.org/wiki/Overclocking#cite_note-1)
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=1)] Considerations
There are several considerations when overclocking. The first consideration is to ensure that it is supplied with adequate power to operate at the new speed. However, supplying the power with improper settings or applying excessive voltage (http://en.wikipedia.org/wiki/Voltage) can permanently damage a component. Since tight tolerances are required for overclocking, only more expensive motherboards—with advanced settings that computer enthusiasts are likely to use—have built-in overclocking capabilities. Motherboards with fewer settings, such as those found in Original Equipment Manufacturer (http://en.wikipedia.org/wiki/Original_Equipment_Manufacturer) (OEM) systems, lack such features in order to eliminate the possibility of misconfiguration and cut down on the support costs and warranty claims to the manufacturer.
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=2)] Cooling
Main article: Computer cooling (http://en.wikipedia.org/wiki/Computer_cooling)
http://upload.wikimedia.org/wikipedia/en/thumb/4/47/Copper_heat_sink_with_pipes.jpg/180px-Copper_heat_sink_with_pipes.jpg (http://en.wikipedia.org/wiki/Image:Copper_heat_sink_with_pipes.jpg) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:Copper_heat_sink_with_pipes.jpg)
High quality heatsinks (http://en.wikipedia.org/wiki/Heatsink) are often made of copper (http://en.wikipedia.org/wiki/Copper).
All electronic circuits (http://en.wikipedia.org/wiki/Electrical_network) produce heat generated by the movement of electrons (http://en.wikipedia.org/wiki/Electron). As clock frequencies in digital circuits (http://en.wikipedia.org/wiki/Digital_circuit) increase, the heat generated by over clocked components also increases. Due to increased heat produced by overclocked components, an effective cooling system is necessary to avoid damaging the hardware. In addition, digital circuits slow down at high temperatures due to changes in metal–oxide–semiconductor field-effect transistor (http://en.wikipedia.org/wiki/MOSFET) (MOSFET) device characteristics. Wire resistance also increases slightly at higher temperatures, contributing to decreased circuit performance.
Because most stock cooling systems are designed for the amount of power produced during non-overclocked use, overclockers typically turn to more effective cooling solutions, such as powerful fans (http://en.wikipedia.org/wiki/Fan_%28mechanical%29) or heavy duty heatsinks (http://en.wikipedia.org/wiki/Heatsinks). Size, shape, and material all influence the ability of a heatsink to dissipate heat. Efficient heatsinks are often made entirely of copper (http://en.wikipedia.org/wiki/Copper), which has a high thermal conductivity (http://en.wikipedia.org/wiki/Thermal_conductivity) but is expensive.[3] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner38-2) Aluminium (http://en.wikipedia.org/wiki/Aluminium) is more widely used; it has poorer thermal conductivity, but is significantly cheaper than copper. Iron (http://en.wikipedia.org/wiki/Iron) and steel (http://en.wikipedia.org/wiki/Steel) are not often used in heatsinks due to their poor thermal conductivity. Silver (http://en.wikipedia.org/wiki/Silver) is used in some designs, its thermal conductivity is higher than copper but it is prohibitively expensive for most applications.[citation needed (http://en.wikipedia.org/wiki/Wikipedia:Citation_needed)] Many heatsinks combine two or more materials to achieve a balance between performance and cost.[3] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner38-2)
http://upload.wikimedia.org/wikipedia/en/thumb/7/7b/DIY_watercooling_T-Line.JPG/180px-DIY_watercooling_T-Line.JPG (http://en.wikipedia.org/wiki/Image:DIY_watercooling_T-Line.JPG) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:DIY_watercooling_T-Line.JPG)
Interior of a water cooled computer, showing CPU water block (http://en.wikipedia.org/wiki/Water_block), tubing and pump
Water cooling (http://en.wikipedia.org/wiki/Water_cooling) and passive liquid coolant (http://en.wikipedia.org/wiki/Coolant) carrying waste heat (http://en.wikipedia.org/wiki/Waste_heat) to a radiator, which is similar to an automobile engine (http://en.wikipedia.org/wiki/Automobile_engine)'s cooling system, provide more effective cooling than heatsink and fan combinations when properly implemented, because liquid is denser than air and therefore offers greater thermal transformation.
Thermoelectric cooling (http://en.wikipedia.org/wiki/Thermoelectric_cooling) devices, also known as Peltier devices, are recently popular with the onset of high Thermal Design Power (http://en.wikipedia.org/wiki/Thermal_Design_Power) (TDP) processors made by Intel and AMD. Thermoelectric cooling devices create temperature differences between two plates by running an electric current (http://en.wikipedia.org/wiki/Electric_current) through the plates. This method of cooling is highly effective but has a drawback that it leads to a lot of excess heat. For this reason, it is often necessary to supplement thermoelectric cooling devices with a convection-based heatsink or a water cooling system.
http://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/2007TaipeiITMonth_IntelOCLiveTest_Overclocking-6.jpg/180px-2007TaipeiITMonth_IntelOCLiveTest_Overclocking-6.jpg (http://en.wikipedia.org/wiki/Image:2007TaipeiITMonth_IntelOCLiveTest_Overclocki ng-6.jpg) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:2007TaipeiITMonth_IntelOCLiveTest_Overclocki ng-6.jpg)
Liquid nitrogen (http://en.wikipedia.org/wiki/Liquid_nitrogen) may be used for cooling an overclocked system, when an extreme measure is needed.
Other cooling methods are forced convection (http://en.wikipedia.org/wiki/Forced_convection) and phase change (http://en.wikipedia.org/wiki/Phase_change) cooling which is used in refrigerators (http://en.wikipedia.org/wiki/Refrigerator). Liquid nitrogen (http://en.wikipedia.org/wiki/Liquid_nitrogen) and dry ice (http://en.wikipedia.org/wiki/Dry_ice) are used as coolants in extreme measures,[4] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner44-3) such as record-setting attempts or one-off experiments rather than cooling an everyday system. These extreme methods are generally impractical in the long term, as they require refilling reservoirs of vaporizing coolant and condensation (http://en.wikipedia.org/wiki/Condensation) is formed on components due to difference between component temperature and air temperature.[4] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner44-3) Moreover, silicon (http://en.wikipedia.org/wiki/Silicon)-based junction gate field-effect transistors (http://en.wikipedia.org/wiki/Junction_gate_field-effect_transistor) (JFET) will degrade below temperatures of roughly 100 K (http://en.wikipedia.org/wiki/Kelvin) (−173 °C (http://en.wikipedia.org/wiki/Celsius)/−280 °F (http://en.wikipedia.org/wiki/Fahrenheit)) and eventually cease to function or "freeze out" at 40 K (−233 °C/−388 °F),[5] (http://en.wikipedia.org/wiki/Overclocking#cite_note-4) so using extremely cold coolants may cause devices to fail.
Submersion cooling, used for Cray-2 (http://en.wikipedia.org/wiki/Cray-2) supercomputer (http://en.wikipedia.org/wiki/Supercomputer), involves sinking a part of computer system directly into a chilled liquid substance that is thermally conductive but sufficiently low in electrical conductivity (http://en.wikipedia.org/wiki/Electrical_conductivity). The advantage of this technique is that no condensation can form on components.[6] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner48-5) A good submersion liquid is Fluorinert (http://en.wikipedia.org/wiki/Fluorinert) made by 3M (http://en.wikipedia.org/wiki/3M), which is expensive and requires permits to purchase it.[6] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner48-5) Another option is mineral oil (http://en.wikipedia.org/wiki/Mineral_oil), but any impurities like water or scenting agents might cause it to conduct electricity.[6] (http://en.wikipedia.org/wiki/Overclocking#cite_note-Wainner48-5)
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=3)] Stability and functional correctness
See also: Stress testing#hardware (http://en.wikipedia.org/wiki/Stress_testing#hardware)
As an overclocked component operates outside of the manufacturer's recommended operating conditions, it may function incorrectly, leading to system instability. An unstable overclocked system, while it may work fast, can be frustrating to use. Another risk is silent data corruption (http://en.wikipedia.org/wiki/Reliability%2C_Availability_and_Serviceability)— errors that are initially undetected. 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 anyone (even the processor manufacturer) to thoroughly test the functionality of a processor. 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 (http://en.wikipedia.org/wiki/Status_register); if the flags are not checked, the error will go undetected. Achieving good fault coverage (http://en.wikipedia.org/wiki/Fault_coverage) requires immense engineering effort, and despite all the resources dedicated to validation by manufacturers, mistakes can still be made. To further complicate matters, in process technologies such as silicon on insulator (http://en.wikipedia.org/wiki/Silicon_on_insulator), devices display hysteresis (http://en.wikipedia.org/wiki/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 speeds 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.[7] (http://en.wikipedia.org/wiki/Overclocking#cite_note-6)
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 a processor-intensive application for testing processors). Popular stress tests include Prime95 (http://en.wikipedia.org/wiki/Prime95), Super PI (http://en.wikipedia.org/wiki/Super_PI), SiSoftware Sandra (http://en.wikipedia.org/w/index.php?title=SiSoftware_Sandra&action=edit&redlink=1), BOINC (http://en.wikipedia.org/wiki/BOINC), Intel Thermal Analysis Tool and Memtest86 (http://en.wikipedia.org/wiki/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 (http://en.wikipedia.org/wiki/Software_testing), the tests are often run for long periods of time, hours or even days.
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=4)] Factors allowing overclocking
http://upload.wikimedia.org/wikipedia/commons/thumb/3/35/Pentium-Dual-Core-E2140-100%25-overclock-2.PNG/180px-Pentium-Dual-Core-E2140-100%25-overclock-2.PNG (http://en.wikipedia.org/wiki/Image:Pentium-Dual-Core-E2140-100%25-overclock-2.PNG) http://en.wikipedia.org/skins-1.5/common/images/magnify-clip.png (http://en.wikipedia.org/wiki/Image:Pentium-Dual-Core-E2140-100%25-overclock-2.PNG)
CPU-Z (http://en.wikipedia.org/wiki/CPU-Z) screenshot demonstrating a 100% overclock of the E2140 (http://en.wikipedia.org/wiki/Intel_Pentium_Dual-Core)
Overclockability arises in part due to the economics of the manufacturing processes of CPUs. In most cases, CPUs with different rated clock speeds are manufactured via exactly the same process. The clock speed that the CPU is rated for is at or below the speed 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 have an excess of similarly high-performing parts and cannot sell them all at the flagship price, so some are marked as medium-speed chips to be sold for medium prices. The performance of a given CPU stepping (http://en.wikipedia.org/wiki/Stepping_%28version_numbers%29) usually does not vary as widely as the marketing clock levels[citation needed (http://en.wikipedia.org/wiki/Wikipedia:Citation_needed)].
When a manufacturer rates a chip for a certain speed, it must ensure that the chip functions properly at that speed over the entire range of allowed operating conditions. When overclocking a system, the operating conditions are usually tightly controlled, making the manufacturer's margin available as free headroom. Other system components are generally designed with margins for similar reasons; overclocked systems absorb this designed headroom and operate at lower tolerances. Pentium architect Bob Colwell (http://en.wikipedia.org/wiki/Bob_Colwell) calls overclocking an "uncontrolled experiment in better-than-worst-case system operation".[8] (http://en.wikipedia.org/wiki/Overclocking#cite_note-7)
Some of what appears to be spare margin is actually required for proper operation of a processor throughout its lifetime. As semiconductor devices (http://en.wikipedia.org/wiki/Semiconductor_device) age, various effects such as hot carrier injection (http://en.wikipedia.org/wiki/Hot_carrier_injection), negative bias thermal instability (http://en.wikipedia.org/w/index.php?title=Negative_bias_thermal_instability&action=edit&redlink=1) and electromigration (http://en.wikipedia.org/wiki/Electromigration) reduce circuit performance. When overclocking a new chip it is possible to take advantage of this margin, but as the chip ages this can result in situations where a processor that has operated correctly at overclocked speeds for years spontaneously fails to operate at those same speeds later. If the overclocker is not actively testing for system stability when these effects become significant, errors encountered are likely to be blamed on sources other than the overclocking.
[edit (http://en.wikipedia.org/w/index.php?title=Overclocking&action=edit§ion=5)] Measuring effects of overclocking
Benchmarks (http://en.wikipedia.org/wiki/Benchmark_%28computing%29) 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).
Given only benchmark scores it may be difficult to judge the difference overclocking makes to the computing experience. For example, some benchmarks test only one aspect of the system, such as memory bandwidth (http://en.wikipedia.org/wiki/Bandwidth), without taking into consideration how higher speeds in this aspect will improve the system performance as a whole. Apart from demanding applications such as video encoding, high-demand databases (http://en.wikipedia.org/wiki/Database) and scientific computing (http://en.wikipedia.org/wiki/Scientific_computing), memory bandwidth (http://en.wikipedia.org/wiki/Memory_bandwidth) is typically not a bottleneck (http://en.wikipedia.org/wiki/Bottleneck_%28engineering%29), so a great increase in memory bandwidth may be unnoticeable to a user depending on the applications they prefer to use. Other benchmarks, such as 3DMark (http://en.wikipedia.org/wiki/3D_Mark) attempt to replicate game conditions, but because some tests involve non-deterministic (http://en.wikipedia.org/wiki/Deterministic) physics, such as ragdoll motion, the scene is slightly different each time and small differences in test score are overcome by the noise floor (http://en.wikipedia.org/wiki/Noise_floor).[citation needed (http://en.wikipedia.org/wiki/Wikipedia:Citation_needed)]
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