Overclocking

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 that of the newest generation of computer hardware.

Users who choose to overclock their components usually focus their efforts on processors, video cards, motherboard chipsets, and Random Access Memory (RAM).

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 in exactly the same way. One important consideration when overclocking a component is to ensure that it is supplied with the proper amount of power for its new speed; however, providing too much power could permanently damage a component. Improper settings carry the potential of destroying the functionality of components, and, in extreme cases, even causing them to catch fire. As a result, only more expensive motherboards--with advanced settings that computer enthusiasts are likely to use--have built-in overclocking capabilities.

Cooling

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 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. Water cooling is often used as well, and when properly implemented provides much more effective cooling than heatsink and fan combinations.

In order to ensure that overclocked components stay at the required temperature, various cooling agents such as 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) are often applied. 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.

In 2003, Tom's Hardware Guide experimented with a Pentium 4 3.4 GHz HT processor, cooling it using liquid nitrogen and forced convection. They managed to achieve over 5 GHz, which is a considerable gain over the original clock speed, and much faster than anything in production at the time. Few users would tolerate regularly topping off their computer with liquid nitrogen, and the noise of such a system makes it impractical for desktop use. 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.5 GHZ Project: CPU Cooling With Liquid Nitrogen, tomshardware.com

Stability

System stability is another major concern when overclocking. A common misconception is that overclocking causes a system to be significantly unstable. Instability is rare, and usually only occurs in cases in which the system is not properly tested with careful temperature and voltage monitoring. Without proper cooling, an overclocked component can overheat, causing the computer to become unstable and potentially unusable. The computer will then 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. Programs such as Super-PI, Prime95, SiSoftware Sandra and Memtest86 are commonplace when executing a stress test.

Root cause

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 with 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 with additional cooling and voltage. 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 the same speed, or faster, than similar CPUs with higher stock clock speeds.

Another explanation for ability for parts and systems to overclock is headroom. Engineers design headroom into components to allow for cushion in their operation. A system requiring 1A of current might be given a power supply which can supply 2A as manufacturing variations in parts might cause the supply to supply a lower maximum current, or the system draw a higher maximum current. Overclocked systems absorb this designed headroom and operate at lower tolerances. Pentium architect Bob Colwell calls overclocking an "uncontrolled experiment in better-than-worst-case system operation". Bob Colwell, "The Zen of Overclocking," Computer, vol. 37, no. 3, pp. 9-12, Mar., 2004.

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 features to detect some errors, but few users are not tolerant of incorrect results. To test if a computer is processing data accurately, test programs that verify their results (rather than simply report a performance score) can be run for long periods.

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, without taking into consideration how faster speeds in this aspect will improve the system performance as a whole. Apart from demanding applications such as video encoding, high-demand databases 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 they prefer to use. Other benchmarks, such as 3DMark 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.

Variance

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. The 4800+ initially carried a 50% price premium over the 4400+.

The extent to which a particular part will overclock is highly variable. Processors from different vendors, production batches, steppings, and invididual units will all overclock to varying degrees.

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 them at prices appropriate to a non-overclocked system at the new speed, the retailer makes more money. In some cases an overclocked component is functionally identical to a non-overclocked one of the new speed, 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 should 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.

Advantages

The user can, in many cases, purchase a slower, cheaper component 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.
Some systems have "bottlenecks", where small overclocking of a component can help realize the full potential of another component to a greater percentage than the limiting hardware is overclocked. For instance, many motherboards with AMD Athlon 64 processors limit the 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 CPU 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.

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 potentially result in damage to the overclocked components.

General disadvantages

These disadvantages are unavoidable by both novices and veterans.

The lifespan of a processor is presumed to be negatively affected by higher operation frequencies, increased voltages and heat. However, 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. One should note that an overclocked system will not generally consume more power than a corresponding non-overclocked system.
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.
High-performance fans used for extra cooling can produce high amounts of noise. Popular models of fans used by overclockers can produce 50 decibels or more. Some people do not mind the extra noise, and it is common for overclockers to have computers much louder than stock machines. Noise can be reduced by utilising strategically placed larger fans which deliver more performance with less noise, or by the use of alternate cooling methods, such as liquid and phase-change cooling.
The heat loss of an overclocked processing unit increases the ambient air temperature of an interior case; consequently, other components may be affected slightly. It is important to note here that a sophisticated cooling configuration has enough potential to subtend this process almost completely.
Overclocking will not necessarily save money. Non-trivial speed increases often require premium cooling equipment to avoid unacceptably high temperatures. It can also become an expensive pastime. Most people who consider themselves overclockers spend significantly more on computer equipment than the average person.
Overclocking has a risky potential to end in a failure ("heat death"). Most companies do not back up defunct units, which are a result of overclocking activities, in their warranties.

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 a quadratic increase. 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 insignificant. The chip itself, or power regulating ICs may overheat 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 specialist recovery tools are not used).
High-power cooling fans can be noisy, and the use of multiple fans requires some knowledge. Without proper thought to placement, turbulence and vortexes may be created in the computer case, resulting in little increase in cooling. In addition, improper mounting may cause rattling or increased vibration.
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 heatsinks designed for chips which do not generate problematic amounts of heat. Novices may spend more money than is necessary.

Limitations

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

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.

Overclocking graphics cards

Graphics cards can also be overclocked, with utilities such as nVidia's Coolbits, or the PEG Link Mode on ASUS motherboards. Overclocking a video card usually shows a much better result in gaming than overclocking a processor or memory. Just like overclocking a processor, sufficient cooling is a must.

Along with the higher clock frequencies come higher temperatures, coupled with the fact that most video cards are sold with coolers designed only to support standard stock temperatures many graphics cards overheat and burn out when overclocked too much.

Prior to irreversible damage to the graphics card, in game distortions known as artifacts become visible and serve as a good warning sign. Two such discriminated "warning bells" are widely understood: green-flashing, random triangles appearing on the screen in 99% of cases correspond to overheating problems on the GPU (Graphics Processing Unit) itself, while white, flashing dots appearing randomly (usually in groups) on the screen mean that the card's RAM (memory) is overheating. It is common to run into one of those problems when overclocking graphics cards. Showing both symptoms at the same time usually means an over-overclocked card (one which is drastically overheating), or poor quality components used to produce the card (in which case the card is not overclockable by any lenghts).

Some overclockers may also make use of a hardware voltage modification where a potentiometer is applied to the video card to give the GPU more voltage and much better overclocking ability. Voltage mods are very risky and usually result in a dead video card. It is also worth mentioning that adding physical elements to the video card immediately voids the warranty (even if the component has been designed and manufactured with overclocking in mind, and has the appropriate section in its warranty). Also, any and all manual hardware modifications which require more than swapping whole components around (soldering a potentiometer to a graphics card is a good example of such action) should be performed by people who feel comfortable with doing it, and prefferably have some technical education in the area. If you're looking to do such a modification but lack the knowledge or expertise, find someone who can help instead of attempting it yourself. Manual modifications are very sensitive in nature, and the process is prone to errors.

The difference between"Unlocking" and "Flashing" a video card

Flashing and Unlocking are ways to gain performance out of a video card, without overclocking it, per se.

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; however, 'flashing' can be difficult and sometimes a bad flash can be irreversible. Sometimes stand-alone software to modify the BIOS files can be found (GeForce 6/7 series are pretty nice in this aspect). It is not required to acquire a BIOS file from a better model video card (although it should be said that the card which BIOS 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 (99% of today's market) have two voltage and speed settings - one for 2D and one for 3D - but were designed to operate with three voltage stages, the third being in the middle between the aforementioned two, serving as a fallback when the card overheats or as a middle-stage when going from 2D to 3D operation mode. Therefore it could be wise to set this middle-stage prior to "serious" overclocking, specifically because of this fallback ability - the card can drop down to this speed, reducing by a few (or sometimes a few dozen, depends on the setting) percent its efficiency, and cool down, without dropping out of the 3D mode (and afterwards return to the desired full-speed clock and voltage settings).

Some cards also have certain abilities not directly connected with overclocking per se. For example, nVidia's GeForce 6600 GT (AGP flavor) features a temperature monitor (used internally by the card), which is invisible for the user in the 'vanilla' version of the card's BIOS. Modifying the card's BIOS (taking it out, changing the value and flashing it back in) can be done in order to make this monitor's value visible for the user (a 'Temperature' tab becomes visible in the card driver's advanced menu).

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

Basically, card 'families' share the same design, even though they run at different speeds and have different features, effectively varying their performance (as it is observed with GeForce 6 series cards, i.e. from LS to vanilla to GT to Ultra). Why? Because creating a completely new design is much, much more expensive than producing the same card and then disabling some of its features and underclocking it (thus making it a more 'budget' model). Besides that, the manufacture process is not perfected, thus some cards come off the bench performing worse than others of the same design (or sometimes with defects), and are then designated as those 'lower cost, slower' versions (i.e. the defective processing pipelines are disabled, and the cards' speed is reduced, and thus from a GeForce 6800 - we get 6800 LS). 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 cards' pervious settings, but it involves manual BIOS flashing using special tools and an identical but original BIOS chip).

External links

Databases:

References

Computer hardware tuning | IBM PC compatibles

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