Overclocking

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Overclocking is the process of forcing a computer component to run at a higher clock rate than designed or designated by the manufacturer.

Overclocking is usually practiced by PC enthusiasts in order to increase the performance of their computers. Some hardware enthusiasts purchase low-end computer components which they then overclock, thereby attaining performance of a high-end system, while others will overclock high-end components, attaining levels of performance that surpass the performance of the newest generation of computer hardware.

Commonly overclocked components include: processors, video cards, motherboard chipsets, and RAM.

1 Considerations for overclocking
- 1.1 Measuring effects of overclocking
2 Overclocking by resellers
3 Advantages
4 Disadvantages
5 Difference between "Unlocking" and "Flashing" a video card
6 See also
7 External links
8 References
- 8.1 Overclocking/Benchmark databases

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Considerations for overclocking

Overclocking allows one to boost a computer system's performance by increasing clock frequencies. There are several methods of overclocking and no two components will overclock the same. One important consideration when overclocking a component is to ensure that it is supplied with the proper amount of power to function properly. However, providing too much power could permanently damage a component. With so many factors affecting how a computer can be overclocked, an improper setting could prove disastrous. As a result, only more expensive motherboards--with advanced settings that computer enthusiasts are likely to use--have built-in overclocking capabilities.

One very important requirement for overclocking a computer is an effective cooling system to remove the excess heat produced by overclocked components. Because most stock cooling systems are designed specifically for the level of heat produced during non-overclocked use, overclockers typically turn to more effective cooling solutions, often employing heavy duty heatsinks and more powerful fans, among other technologies. Water cooling is often used as well, and when properly implemented provides much more effective cooling than heatsink/fan combinations.

Methods that have been used to cool overclocked components include: forced convection (a fan blowing across a surface); Liquid Cooling (liquid coolant carrying waste heat to a radiator, similar to an automobile engine); liquid nitrogen; dry ice; phase change cooling (as used in refrigerators); and submersion (placing the entire computer in an inert fluid). In most cases liquid nitrogen is only a temporary cooling measure because keeping nitrogen coolant in a liquid state is usually quite uneconomical. Because of this, liquid nitrogen (or dry ice, for that matter) is usually used only as an extreme measure to aid in setting a record in a one-off experiment (destroying the cooled hardware in most cases) rather than for cooling an everyday system. Of the aforementioned methods, air cooling, liquid cooling, and phase cooling are the most popular, due to their efficiency, availability, and affordability.

System stability is another major concern when overclocking. A commonly held view is that overclocking causes a system to be significantly unstable. This is rarely the case when the system is properly tested with careful temperature and voltage monitoring. Without proper cooling, an overclocked component can overheat, causing the computer to crash, freeze or hang; in other words, become unstable and potentially unusable. The computer will have to be reset and underclocked, or given a voltage increase or better cooling. Stress tests (or "torture tests") can be used to test a system's stability by placing a high load on overclocked components, often for several hours or even days. Commonly-used programs for stress testing are Super-PI, Prime95, SiSoftware Sandra and Memtest86.

Overclocking 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 marketed under is the speed at which the CPU has been tested to consistently operate well, but often processors can operate at frequencies substantially higher than stated in the specifications. There are, however, CPUs that are actually at their physical processing limit i.e. they cannot operate at higher frequencies correctly. With proper power and cooling, slower CPUs may be made to run at literally the same speed, or faster, than similar CPUs with higher stock clock speeds.

There have been situations in which a chip manufacturer will deliberately underrate a chip in response to market pressure. This results in an inexpensive component that (with a little extra voltage) is easily overclocked to match the speed of a more expensive component. One example is the AMD Athlon 64 X2 4400+ (codename Toledo) processor, which was easily made as fast as the AMD Athlon 64 X2 4800+, simply by increasing the voltage and clock speeds. Manufacturers will often sell these processors at 50% extra. Users can often easily overclock a component to above the highest settings a manufacturer will sell a component for.

Recently computer experts experimented with a Pentium 4 3.4 GHz HT processor, cooling it using liquid nitrogen, and blowing cold air at high speeds past it. They managed to achieve over 3 GHz above the original frequency, which is a considerable amount. Few users would tolerate regularly topping off their computer with liquid nitrogen, the noise alone of such a system making it impractical. These tests are interesting, however, as an illustration of what is possible when great amounts of heat can be removed from a system and are an indication of what could be achieved with better (but not as drastic) cooling.

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Measuring effects of overclocking

For some overclockers, the increased clock statistics are a reward in themselves, while others take the more pragmatic view that perceptible improvements are necessary to justify the effort. Human judgment on the speed of a computer is inherently subjective and open to the placebo effect, therefore there are many de facto benchmarks used to evaluate performance. The benchmarks can themselves become a kind of 'sport', in which users compete for the highest scores. Whilst an overclocked computer may seem stable to the user, and may pass certain tests, the computer may process data incorrectly. Operating systems and programs have a margin of error to cope with incorrect data processing, some programs however cannot allow this. Such is the case with Folding@Home distributed computing software, where data needs to be accurate otherwise it is rendered useless. To test if a computer is processing data accurately, benchmarking needs to be set continuously for days. Given only benchmark scores it may be difficult to judge the difference overclocking makes to the computing experience. Some benchmarks test only one aspect of the system, such as memory bandwidth, without taking into consideration how faster speeds in this aspect will improve the system performance as a whole; memory bandwidth is typically not a bottleneck, apart from 'serious tasks' like video encoding, high-demand databases and scientific computing. Other benchmarks, such as 3D Mark attempt to replicate game conditions, but because some tests involve non-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. Most overclocking sites use recorded demos of recent games for benchmarks, which give a good indication of the performance in that game, but are still not completely realistic because the system does not have to perform physics calculations. Programs such as 3D Mark 2001/2001 SE are highly recommended for testing out CPU overall performance as the 3D Mark 2001 and 2001 SE tend to be more CPU senative and scores can vary more depending on the CPU than the VGA card. As for an overall gaming experience benchmark, 3D Mark 2003, 3D Mark 2005, 3D Mark 2006 can all be used, in general these 3 programs are less sensative to CPU instead more on the VGA card performance. However due to the recent release of 3D Mark 2006, it tends to favour Dual Core CPUs and Nvidia based VGA cards. This could be because of the addition High Definition (HD) display tests which is more suitable for the Dual Core CPUs operate under. For people who are not into VGA card overclocking but more on the CPU and RAM overclocking, Super PI or Super PI MOD will be the perfect program to measure your CPU and RAM speed. Super PI is the program inwhich the computer will have to calculate an amount of data of PI, the lower the better. In most cases, 1Mb is the most commonly use for benching. For an average AMD system, you will be looking for score of about 40 seconds.

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Overclocking by resellers

Commercial system builders or component resellers sometimes overclock to sell items at higher profit margins. By buying lower-value components, overclocking them, and selling on as higher value ones, the retailer makes more money. In some cases an overclocked component is functionally identical to a factory-clocked one, especially if it was deliberately underrated by the manufacturer; however, it is generally considered dishonest if the customer is not told they are buying overclocked equipment. It is felt that because of a risk of shortened component lifespan, the customer be allowed the informed choice to use overclocked components or not.

Overclocking is sometimes seen as a legitimate service, in which a company tests the 'overclockability' of individual items rather than the customer just buying and hoping theirs will overclock well. One example is the retailer who checks which GeForce 6800 cards work correctly with extra pixel shaders unlocked (effectively making it a 6800 ultra), and charges slightly above the retail price for the cards known to work. Many specific 'tricks of the trade' such as this are highly dangerous and can render hardware non-functional, though they are still attractive since, as with all overclocking, the user is getting a 'free lunch'. Simple feature unlocking such as this can often be done by simply joining two points on a circuit with a graphite pencil (known as the pencil trick)

Of course, manufacturers would like high performance seekers to pay extra for high-end products, but also fear that less reliable components and shortened life span would damage brand image. It is mainly fear of this kind of practice that motivates major manufacturers to design overclocking prevention mechanisms such as CPU locking. These measures are claimed to be customer protection, which often meets a mixed reception.

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Advantages

The user can, in many cases, purchase a slower component for a cheaper price and overclock it to the speed of a more expensive component. (Although the possibility of decreasing the component's lifespan makes the argument of expense dual-sided. see Disadvantages below.)
Faster performance in games, applications, and system tasks at no additional expense.
Small overclocking of a component can help realize the full potential of another component to a greater percentage than the limiting hardware is overclocked. For instance, many motherboards with AMD Athlon 64 processors limit the speed of four units of RAM to 333 MHz. However, the memory speed is computed by dividing the processor speed (which is a base number times a multiplier, for instance 1.8 GHz is most likely 9x200 MHz) by a fixed integer such that, at stock speeds, the RAM would run at a clock rate near 333 MHz. Manipulating elements of how the processor speed is set (usually lowering the multiplier), one can often overclock the processor a small amount, around 100-200 MHz (less than 10%), and gain a RAM clock rate of 400 MHz (20% increase), realizing the full potential of the RAM.
Overclocking can be an engaging hobby in itself and supports several dedicated online communities.

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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 introduces many avoidable drawbacks.

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General disadvantages

These disadvantages are unavoidable by both novices and veterans.

The lifespan of a processor is negatively impacted by higher operation frequencies, increased voltages and heat. However, the effect of operation frequencies and voltages has not been proven to be a major factor in processor lifespan. An experienced overclocker would have taken steps to ensure operation within safe temperature ranges. Moreover, with the rapid obsolescence of processors coupled with the long life of solid state microprocessors (10 years or more), it is argued that the processor will be replaced before any threat of failure.
An increase in clock speeds and sometimes voltages results in higher power consumption and a higher power bill.
While systems may be thoroughly tested for stability before usage, stability problems may surface after prolonged usage due to an unusual workload or untested portions of the processor core. Although this is rare, such incidents may result in data loss.
An easy method of managing heat is the use of high performance fans which produces a high amount of noise. A popular make of fan for overclockers, the delta focus flow, can produce 50 decibels or more. This is unacceptably loud for a desktop computer for prolonged use. Properly managed, this issue can be reduced by utilising strategically placed larger fans which deliver more performance with less noise, or by the use of alternate cooling methods. Quieter options for overclockers include liquid and phase-change cooling.
Overclocking will not necessarily save money. Non-trivial speed increases often require premium cooling equipment or running components at an unacceptably high temperature. It can also become an expensive pastime. Most people who consider themselves overclockers spend significantly more on computer equipment than the average person. As always, it is important to spend money prudently, by purchasing components that would alleviate the greatest bottlenecks or roadblocks to higher frequency operation.

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Disadvantages of overclocking by novices

Increasing the operation frequency of a component will increase its thermal output in a linear fashion, while an increase in voltage causes an exponential increase. Furthermore, semiconductor physics dictate that higher temperatures results in a higher resistance. Improperly managed, a novice may cause chip temperatures to rise so quickly that a permanent decrease in life expectancy or irreversible damage is caused to the chip.
With the advent of ever wider ranges of voltage options on motherboards, the risk of fire or burns is not tiny. The chip itself, or power mosfets may burn and capacitors may burst.
More common than hardware failure is instability. Although the hardware is not permanently damaged, this is inconvenient and could cause data loss. In rare, extreme cases entire filesystem failure may occur, causing the loss of all data. (If specialized recovery tools are not used)
The indiscriminate use of powerful fans usually creates a lot of noise. Novices may add too many fans in incorrect positions. Without proper thought to placement, turbulence and vortexes may be created in the computer case, further aggravating the situation without much increase in cooling. In addition, improper mounting may cause rattling or increased vibration. Some people do not mind the extra noise, and it is common for overclockers to have computers much louder than stock machines. Quieter options for overclockers include liquid and phase-change cooling.
Improper installation of exotic cooling solutions like liquid or phase-change cooling may result in failure of the system, which may result in water damage or damage to the processor due to the sudden loss of cooling.
Products sold specifically for overclocking are sometimes just decoration. Although this is not a bad thing in itself, novice buyers should be aware of the marketing hype surrounding some products. Examples include heat spreaders and Heatsink designed for chips which do not generate problematic amounts of heat. Novices may spend more money than is necessary.

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Limitations

While overclocking is beneficial to some tasks, it too is limited by many factors.

Not every component of a computer is overclockable; for example, hard drive platters can have an increased rpm rate by overvolting the drive motor, but this often leads to the destruction of the drive; or hard drive corruption. Where hard drive read/write rate is the bottleneck, as it often is, overclocking brings little or no speed advantage. There are also cases in which overclocking is possible, but the risk of doing so is unacceptable (as in the hard drive example, where any possibility of data loss cannot be tolerated).
Personal computers are mostly used for tasks which do not push the hardware, or where the speed of a task is restricted by bottlenecks outside of the local machine. For example, web browsing does not require a very fast computer, and the limiting factor will almost certainly be the speed of the internet connection. Other general office tasks such as word processing and sending email are more dependent on the efficiency of the user than on the speed of the hardware. In these situations any speed increases through overclocking are unlikely to be noticeable.
It is generally accepted that, even for computationally-heavy tasks, speed increases of less than ten percent are difficult to discern. For example, when playing video games, most people would fail to notice an increase from 60 to 66 frames per second without the aid of an on-screen frame counter. Generally, gains of a few percent are sought for prestige rather than real-world computational benefit. In some cases, the risks outweigh the gains.

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Difference between "Unlocking" and "Flashing" a video card

Flashing and Unlocking are ways to gain performance out of a video card, without per se overclocking it. Flashing is taking the BIOS of another card, based on the same core and design specs, and using it to "override" the original BIOS, thus effectively making it a higher model card; but be warned, Flashing can be difficult and sometimes a bad flash can be irreversible.

Unlocking would be taking a card and unlocking pipelines and/or pixel shader. This is commonly done on the 6800LE and 6800 (AGP models only). While the 6800LE and 6800 have 8 and 12 pipes respectively, they share the same core as a 6800GT or Ultra, but may not have passed with the extra pipelines and vertex shaders unlocked.

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