Overclock

What Is Overclocking?

Introduction

Many people probably don't know what overclocking is but have possibly heard the term used before. To put it in its simplest terms, overclocking is taking a computer component such as a processor and running at a specification higher than rated by the manufacturer. Every part produced by companies such as Intel and AMD are rated for a specific speeds. They have tested the capabilities of the part and certified it for that given speed. Of course, most parts are underrated for increased reliability. Overclocking a part simply takes advantage of the remaining potential out of a computer part that the manufacturer is unwilling to certify the part for but it is capable of.

Why Overclock a Computer?

The primary benefit of overclocking is additional computer performance without the increased cost. Most individuals who overclock their system either want to try and produce the fastest desktop system possible or to extend their computer power on a limited budget. In some cases, individuals are able to boost their system performance 25% or more! For example, a person may buy something like an AMD 2500+ and through careful overclocking end up with a processor that runs at the equivalent processing power as a AMD 3000+, but at a greatly reduced cost.

There are drawbacks to overclocking a computer system. The biggest drawback to overclocking a computer part is that you are voiding any warranty provided by the manufacturer because it is not running within its rated specification. Overclocked parts that are pushed to their limits also tend to have a reduced functional lifespan or even worse, if improperly done, can be destroyed completely. For that reason, all overclocking guides on the net will have a disclaimer warning individuals of these facts before telling you the steps to overclocking.

Bus Speeds and Multipliers

To first understand overclocking a CPU in a computer, it is important to know how the speed of the processor it computed. All processor speeds are based upon two distinct factors, bus speed and multiplier.

The bus speed is the core clock cycle rate that the processor communicates with items such as the memory and the chipset. It is commonly rated in the MHz rating scale referring to the number of cycles per second that it runs at. The problem is the bus term is used frequently for different aspects of the computer and will likely be lower than the user expects. For example, an AMD XP 3200+ processor uses a 400 MHz DDR memory, but the processor is in fact using a 200MHz frontside bus that is clock doubled to use 400 MHz DDR memory. Similarly, the new Pentium 4 C processors have an 800 MHz frontside bus, but it is really a quad pumped 200 MHz bus.

The multiplier is the multiple that the processor will run at compared to the bus speed. This is the actual number of processing cycles it will run at in a single clock cycle of the bus speed. So, a Pentium 4 2.4GHz "B" processor is based on the following:

133 MHz x 18 multiplier = 2394MHz or 2.4 GHz

When overclocking a processor, these are the two factors that can be used to influence the performance. Increasing the bus speed will have the greatest impact as it increases factors such as memory speed (if the memory runs synchronously) as well as the processor speed. The multiplier has a lower impact than the bus speed, but can be more difficult to adjust.

Let's look at an example of three AMD processors:

CPU Model	Multiplier	Bus Speed	CPU Clock Speed
Athlon XP 2500+	11x	166 MHz	1.83 GHz
Athlon XP 2800+	12.5x	166 MHz	2.08 GHz
Athlon XP 3000+	13x	166 MHz	2.17 GHz
Athlon XP 3200+	11x	200 MHz	2.20 GHz

Let's then look at two examples of overclocking the XP2500+ processor to see what the rated clock speed would be by changing either the bus speed or the muliplier:

CPU Model	Overclock Factor	Multiplier	Bus Speed	CPU Clock
Athlon XP 2500+	Bus Increase	11x	(166 + 34) MHz	2.20 GHz
Athlon XP 2500 +	Multiplier Increase	(11+2)x	166 MHz	2.17 GHz

In the above example, we have done two changes each with a result that places it at either the speed of the 3200+ or a 3000+ processor. Of course, these speeds are not necessarily possible on every Athlon XP 2500+. In addition, there may be a large number of other factors to take into consideration to reach such speeds.

Because overclocking was becoming a problem from some unscrupulous dealers who were overclocking lower rated processors and selling them as higher priced processors, the manufacturers started to implement hardware locks to make overclocking more difficult. The most common method is through clock locking. The manufacturers modify traces on the chips to run only at a specific multiplier. This can still be defeated through modification of the processor, but it is much more difficult.

Voltages

Every computer part is regulated to specific voltages for their operation. During the process of overclocking the parts, its possible that the electrical signal will be degraded as it traverses the circuitry. If the degradation is enough, it can cause the system to become unstable. When overclocking the bus or multiplier speeds, the signals are more likely to get interference. To combat this, one can increase the voltages to the CPU core, memory or AGP bus.

There are limits to the amount of additional voltage that can be applied to the processor. If too much voltage is applied, the circuits inside the parts can be destroyed. Typically this is not a problem because most motherboards restrict the possible voltage settings. The more common problem is overheating. The more voltage supplied, the higher the thermal output of the processor.

HEAT!

The biggest obstacle to overclocking the computer system is heat. Today's high-speed computer systems already produce a large amount of heat. Overclocking a computer system just compounds these problems. As a result, anyone planning to overclock their computer system should be very aware of the needs for high performance cooling solutions.

The most common form of cooling a computer system is through standard air cooling. This comes in the form of CPU heatsinks and fans, heat spreaders on memory, fans on video cards and case fans. Proper airflow and good conducting metals are key to the performance of air cooling. Large copper heatsinks tend to perform better and the greater number of case fans to pull in air into the system also helps to improve cooling.

Beyond air cooling there is liquid cooling and phase change cooling. These systems are far more complex and expensive than standard PC cooling solutions, but they offer a higher performance at heat dissipation and generally lower noise. Well-built systems can allow the overclocker to really push the performance of their hardware to its limits, but the cost can end up being more expensive than processor to begin with. The other drawback is liquids running through the system that can risk electrical shorts damaging or destroying the equipment.

Component Considerations

Throughout this article we have discussed what it means to overclock a system, but there are a lot of factors that will affect whether a computer system can even be overclocked. The first and foremost is a motherboard and chipset that has a BIOS that allows the user to modify the settings. Without this capability, it is not possible to modify the bus speeds or multipliers to push the performance. Most commercially available computer systems from the major manufacturers do not have this capability. This is why most people interested in overclocking tend to buy specific parts and build their own systems or from integrators who sell the parts that make it possible to overclock.

Beyond the motherboards ability to adjust the actual settings for the CPU, other components must also be able to handle the increased speeds. Cooling has already been mentioned, but if one plans on overclocking the bus speed and keeping the memory synchronous to offer the best memory performance, it is important to buy memory that is rating or tested for higher speeds. For example, overclocking an Athlon XP 2500+ frontside bus from 166 MHz to 200 MHz requires that the system have memory that is PC3200 or DDR400 rated. This is why companies such as Corsair and OCZ are very popular with overclockers.

The frontside bus speed also regulates the other interfaces in the computer system. The chipset uses a ratio to reduce the frontside bus speed to run at the speeds of the interfaces. The three major desktop interfaces are AGP (66 MHz), PCI (33 MHz) and ISA (16 MHz). When the frontside bus is adjusted, these buses will also be running outside of specification unless the chipset BIOS allows for the ratio to be adjusted down. So it is important to know how adjusting the bus speed can impact stability through the other components. Of course, increasing these bus systems can also improve performance of them, but only if the components can handle the speeds. Most expansion cards are very limited in their tolerances though.

Slow and Steady

Now those who are looking to actually do some overclocking should be warned not to push things too far right away. Overclocking is a very tricky process of trial and error. Sure a CPU may be able to be greatly overclocked in the first try, but it is generally better to start out slow and gradually work the speeds up. It is best to test the system fully in a taxing application for an extended period of time to ensure the system is stable at that speed. This process is repeated until the system does not test fully stable. At that point, step things back a bit to give some headroom to allow for a stable system that has less chance of damage to the components.

Conclusions

Overclocking is a method for increasing performance of standard computer components to their potential speeds beyond the rated specifications of the manufacturer. The performance gains that can be obtained through overclocking are substantial, but a lot of consideration must be done before taking the steps to overclocking a system. It is important to know the risks involved, the steps that must be done to obtain the results and a clear understanding that results will very greatly. Those who are willing to take the risks can get some great performance from systems and components that can end up being far less expensive than a top of the line system.

For those who want to do overclocking, it is highly recommended to do searches on the Internet for information. Researching your components and the steps involved are very important to being successful.

Remote Sensing

The technology of modern remote sensing began with the invention of the camera more than 150 years ago. Although the first, rather primitive photographs were taken as "stills" on the ground, the idea and practice of looking down at the Earth's surface emerged in the 1840s when pictures were taken from cameras secured to tethered balloons for purposes of topographic mapping. Perhaps the most novel platform at the end of the last century is the famed pigeon fleet that operated as a novelty in Europe. By the first World War, cameras mounted on airplanes provided aerial views of fairly large surface areas that proved invaluable in military reconnaissance. From then until the early 1960s, the aerial photograph remained the single standard tool for depicting the surface from a vertical or oblique perspective.

Satellite remote sensing can be traced to the early days of the space age (both Russian and American programs) and actually began as a dual approach to imaging surfaces using several types of sensors from spacecraft. In 1946, V-2 rockets acquired from Germany after World War II were launched to high altitudes from White Sands, New Mexico. These rockets, while never attaining orbit, contained automated still or movie cameras that took pictures as the vehicle ascended. Then, with the emergence of the space program in the 1960s, Earth-orbiting cosmonauts and astronauts acted much like tourists by taking photos out the window of their spacecraft.

The term "remote sensing," first used in the United States in the 1950s by Ms. Evelyn Pruitt of the U.S. Office of Naval Research, is now commonly used to describe the science—and art—of identifying, observing, and measuring an object without coming into direct contact with it. This process involves the detection and measurement of radiation of different wavelengths reflected or emitted from distant objects or materials, by which they may be identified and categorized by class/type, substance, and spatial distribution.

Overclocking

OVERCLOCKING

Description:

Overclocking is the somewhat unknown and uncommon practice of running your CPU (or other parts) past the speed that it is rated at. An example is running a 1.2 GHz CPU at 1.4 GHz or a 200 MHz CPU at 233 MHz. How can this be achieved? The following description isn't exact, but it captures the basic idea. Most CPU companies create their CPUs and then test them at a certain speed. If the CPU fails at a certain speed, then it is sold as a CPU at the next lower speed. The tests are usually very stringent so a CPU may be able to run at the higher speed quite reliably. In fact, the tests are often not used at all. For example, once a company has been producing a certain CPU for awhile, they have gotten the process down well enough that all the CPUs they make will run reliably at the highest speed the CPU is designed for. Thus, just to fill the demand, they will mark some of them as the slower CPUs.
Beware, however, that some vendors may sell CPUs already overclocked. This is why it is very important to buy from a dealer you can trust.
Some video cards are also very overclockable with some companies selling their cards already overclocked (and advertised this way). The Programs like Powerstrip can often be used to easily overclock the cards.
Also, if you're afraid to overclock your CPU, let another company do it for you! Companies like ComputerNerd sell CPUs pretested at overclocked speeds.

What To Consider:

• Do you NEED to overclock? It may not be worth the risk if your computer is running fine as it is. However, if it seems a little too slow and/or you're a speed freak, it may be worth the risk.
• How important is your work? If you're running a very important network server, it may not be worth it to put the extra strain on the computer. Likewise, if your computer does a lot of highly CPU intensive operations, you may also want to not overclock. Obviously the most stable computer is going to be one that is not overclocked. This is not to say that an overclocked computer can not be 100% stable because they CAN. If you just use your computer to play games and would like to have a little faster frame rates, then overlcocking may be worth it.

Potential Side-Effects?

• The first impression people usually have of overclocking is "isn't that dangerous?" For the most part, the answer is no. If all you do to try to overclock your computer is change the CPU's speed, there is very little chance that you will damage your computer and/or the CPU as long as you do not push your computer too hard (i.e. trying to run a 500 MHz CPU at 1 GHz. Damage has happened, but it's a rare thing. Also, if you start increasing voltage settings to allow your CPU to run at a higher speed, there is more of a risk there.
• The best way to prevent damage is to keep your CPU as cool as possible. The only way you can really damage your CPU is if it gets too hot. Adequate cooling is one of the keys to successful overclocking. Using large heatsinks with powerful ball-bearing fans will help to achieve this. How hot is too hot? If you can't keep your finger on the CPU's heatsink comfortably, then it is probably too hot and you should lower the CPU's speed.
• Changing the bus speed is actually more beneficial than changing the CPU's speed. The bus speed is basically the speed at which the CPU communicates with the rest of the computer. When you increase the bus speed, in many cases you will be overclocking all the parts in your AGP, PCI slots, and your RAM as well as the CPU. Usually this is by a small margin and won't hurt these components. Pay attention to them though. If they're getting too hot, you may need to add extra cooling for them (an additional fan in your case). Just like your CPU, if they get too hot, they may be damaged as well.

Difficulty Level:

• Believe it or not, it's actually quite simple. In many cases all you have to do is change a couple of jumpers on the motherboard or change settings in your motherboard's BIOS.

Recommendations:

• Most of today's CPUs are multiplier locked, but you can change the bus speed. As an example, you could run a 1.2 GHz Thunderbird that normally runs at 133 bus (also called 266 because it is "double-pumped) at:
• Multiplier * Bus Speed = CPU speed in MHz
• 9 * 133 = 1,200 MHz = 1.2 GHz = default
• 9 * 140 = 1,260 MHz = 1.26 GHz
• 9 * 145 = 1,305 MHz = 1.3 GHz
• 9 * 150 = 1,350 MHz = 1.35 GHz

Even though that CPU is multiplier locked, you can change the multiplier by connecting the "L1" dots on the CPU itself with a normal pencil (it's just enough to conduct electricity to allow you to change the multipliers). If you do this properly, it is perfectly safe. Here's an article on how to do this.

• 9 * 133 = 1,200 MHz = 1.2 GHz = default
• 9.5 * 133 = 1,264 MHz = 1.264 GHz
• 10 * 133 = 1,333 MHz = 1.333 GHz
• Or change both together, like this:
  10 * 140 = 1,400 MHz = 1.4 GHz
• All you need to do here is use common sense really. For example, you wouldn't want to try to run a 233 MHz CPU at 400 MHz. For one thing, it won't work. For another, that probably would damage your CPU. I would advise starting out low and slowly trying to go higher. If you have a 233 MHz CPU, try running it one step higher, then the next step. Most likely you won't be able to get a CPU like this to run much higher than 300, but that is a possibility.
• Be more concerned with changing the bus speed than the CPU speed as that will provide the greatest amount of speed improvement. For example, running a CPU at 250 (83.3x3) would be better than 262.5 (75x3.5) in most cases because the bus speed of 83 is higher than 75. The default for most CPUs is at 66 MHz bus speed. The newer P2's bus speed is 100 MHz by default. Many computers will not have options on bus speeds, but if you get any of the motherboards I recommend, you will have different bus speed options. The higher bus speed you can run at reliably, the better. Depending on what your other components are though, they may cause your computer to crash or become unstable if they can't handle the higher bus speeds. With bus speeds like 133, you have to have higher quality PC133 or PC2100 DDR SDRAM to be able to achieve this bus speed reliably.

What you'll need:

An open computer case and your motherboard manual is all you'll really need to try it, but more efficient cooling may be useful as well. Of course, your motherboard needs to support the bus speeds you plan to use and the multiplier you plan to use. Your motherboard manual should tell you whether or not it supports certain bus speeds and certain multipliers. If the exact CPU speed using a particular multiplier and bus speed isn't listed, don't worry. If you have the proper multiplier and bus speed in your manual, then you should be okay.

How to calculate your desired speed:

• First consider your default speed. For simplicity, lets say it's 1 GHz. If this is an Athlon processor, it would most likely be running at the 133 MHz bus speed with a multiplier of 7.5 (100x7.5 = 1000 MHz = 1 GHz) or at the 100 MHz bus speed and multiplier of 10 (10x100 = 1000). Let's use the latter instance as an example - 100 MHz bus and 10 multiplier.
• If you wanted to run at around 1.2 GHz you could increase the multiplier to 12 and leave the bus speed alone (100x12 = 1200). *Please note* most of today's CPUs prevent you from changing the multiplier and only allow you to change the bus speed! The step below explains how to do this.
• If you wanted to increase the bus speed and the motherboard supported the higher MHz bus speeds, you could do something like 10x120 for 1200 MHz. Calculate your new speed by multiplying the bus speed by your CPU's multiplier.
• You could also try increasing both the bus speed and multiplier. An example would be increasing the multiplier to 11 and bus speed to 110 MHz for just over 1.2 GHz (11x110 = 1210 MHz).

How to SET this speed:

• In your motherboard manual, find the jumper settings for the particular bus speed and multiplier you want to use. Locate those jumpers on your motherboard and change them to fit the jumper settings in the manual. If it says "closed" for a jumper, then you need to have the little "shunt" placed over the two pins for that jumper which "closes" the connection. If it says "open" you may need to pull off the shunt.
• If your motherboard has a "SoftMenu," then you can change your bus speed and / or multiplier in the computer's BIOS. Usually you will have to press F1 or Del to enter your BIOS while your computer is starting up. Try to locate the CPU speed settings and rotate through the available bus speeds until you find the one you are wanting to try.
• Some motherboards will have both jumpers and a SoftMenu and you can use either one. Others have a combination and you may need to change the bus speed on the motherboard with jumpers, and change the multiplier in the BIOS. That's all there is to it!

If the speed you're trying to run at won't work for some reason, then some of these quick-fix solutions may help...

1. Add additional cooling if your CPU is getting too hot. A fan blowing on the fan that's on the CPU can help. You could also try a bigger/better heatsink and fan combo or a Peliter effect cooler which basically works as a refrigerant for your CPU. Using thermal grease to seal the connection and enhance heat transfer between your CPU and heatsink can also be very helpful.
2. Though it can be dangerous if you go too high, you may want to try increasing the voltage. Not all motherboards support this option though. Do so in small steps if you can and avoid going more than four or five tenths of a volt higher. Make sure your CPU isn't getting too hot as you try this.
3. Sometimes the CPU's cache won't tolerate the higher speeds. Although I wouldn't suggest this to increase performance because it would have the opposite effect, you can disable your CPU's cache in the BIOS just to try to find out if that is what is preventing you from reaching a higher speed. Then change it back later.
4. If you're running a Pentium II and it won't let you run at the 100 MHz bus speed or higher, try to cover up the B21 pin on the CPU. Tom's Hardware Guide has a good description of this. The same applies to the Celeron CPUs.
5. If you have an older hard drive ('97 or earlier), consider lowering the PIO mode in the BIOS as the hard drive may not like the faster bus speed.
6. Adjust memory timings in your BIOS. Take them as low as you can without losing stability in an UNoverclocked situation, then try them in an oveclocked situation. You may have to have slower speeds for your memory to be able to overclock (i.e. run your RAM at CAS 3 when overclocking and CAS 2 when not). CAS 3 would be much slower, but it may allow you to run your CPU faster (and tell you to get faster RAM that will run the higher bus speeds at CAS 2.
7. If you run one of the first Athlon CPUs, look for a "Golden Fingers" card to allow you to overclock the CPU.
8. Here's a long but important note on PCI and AGP cards. If, for example, your system runs at 133 MHz bus speed by default, then increasing your bus speed to 166 overclocks your RAM, PCI cards, and AGP card. At 133, your PCI cards run at 1/4 the bus speed (33 MHz, which is default). At 166, the divisor may remain at 1/4 in which case your PCI cards are overclocked to 41.5 MHz. This may be okay for most PCI devices, but some may have problems. See if your motherboard has a 1/5 divisor for PCI (PCI would then run at the default 33 MHz).
   For AGP (usually more important because AGP more often has problems with higher speeds) the problem is similar. AGP is supposed to run at 66 MHz. At 133 bus, AGP is configured by 1/2 the bus speed (133 * 1/2 = 66). When running at 166 MHz bus speed, your AGP card may overclocked to 83 MHz, which may be too much. If a ratio of 2/5 is supported by your motherboard, then the AGP speed would be at default (166 * 2/5 = 66 MHz).