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: 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: 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:
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
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
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. 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. The following section describes how overclocking may be done using the BIOS. Enter the BIOS during system startup. Select the Bios Features Setup, CPU Soft Menu or any other similar option and press Enter. Modify the CPU Host Bus Frequency, External Clock (PCI) or similar option shown with Page Down until you find the motherboard FSB speed you want (for example 200 MHz for processors whose FSB normally works at 166 MHz). In the CPU Core section find the Multiple Bus Frequency or Multiplier factor and modify the value of the CPU Multiplier (for example 11x may be changed to 13x). Now save the changes to the CMOS and exit.It is generally advisable to change the parameters in steps. For example increase the FSB speed by a few MHz and check whether the system boots. If your computer boots increase the speed further and check again. Repeat until you have the highest setting with which your computer will boot up. Now test your OS with some resource hungry application say a game, to check whether the system crashes. If it crashes lower the FSB speed in steps till the point where the system is stable.
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.
How do I overclock my pc?:
Overclocking results in change to the voltage profile within the circuitry. This can be minimized by increasing the voltages applied but too much increase can burn up the circuitry. A bigger problem is the heat generated due to overclocking. This is tackled through the use better CPU heatsinks and fans, heat spreaders on memory, fans on video cards and case fans.
