Overclocking Info

Warning: We neither advise for nor against overclocking a microprocessor. Overclocking is not for everyone. Successful overclocking will require some technical knowledge and a great deal of homework and planning. Overclocking a processor may void the warranty. Do it at your own risk.

What is clock speed for a processor?

Clock speed is one of the main factors that determine the computing power of a computer. It is measured in MHz. The higher the number the higher the speed. The clock speeds in the current market range from 233MHz to 1000 MHz (1GHz) (second quarter of 2000).

Here is an analogy that will help you understand the concept. Imagine your car drives at fixed speeds of 10, 20, 30?200 MPH. While the car and the speed limit may be designed to optimally run at 60MPH, nothing prevents you from running it at speeds lower or higher than 60MPH. Of course, you want to run at higher speeds only at favorable conditions.

How CPU manufacturers determine the clock speed of a processor?

The above analogy suggests that the clock speeds of a microprocessor may be arbitrary. That's actually correct! The manufacturer decides on what speed to stamp on the processor based on the following factors: (1) The core structure, design, and capabilities of the processor itself. (2) The thermal stability and characteristics of the processor. (3) The market conditions.

Here are more explanations that will help you understand the process.
  1. A classic Intel Pentium processor runs between 66 and 200MHz. That's the limitation set up by the design and the technology behind the processors. Manufacturers overcome this limitation by redesigning the processor. As a result, you have Pentium MMX, Pentium II, Pentium III, and Pentium IV. These different "levels" of the processors are incompatible among each other while the clock speeds get higher and higher. Nowadays there are even different "breeds" among the same level of processors, making them incompatible. For instance, there are three types of Pentium III on the market: non-Coppermine (conventional) Slot 1, Coppermine Slot 1, and flip-chip PGA.

     
  2. A processor coming out of the production line is tested for the highest clock speed allowed with a pre-set of conditions for stability. The same batch of processors with the exactly same design and structure may be marked for different clock speeds because of the difference in thermal characteristics that cannot be totally controlled or reproduced in the manufacturing process. In other words, Intel Pentium III 600 and 650MHz may be structurally and materially identical. Take notice that the manufacturer testing is performed with "average" thermal conditions to meet the needs for an average market. Under better thermal conditions, the processor should be able to run stably at higher speeds.

     
  3. For obvious reasons the manufacturer wants to sell as many high speed processors as possible. Therefore, they want to have high through-put in fabricating high-speed processors as long as the manufacturing cost is the same. However, sometimes the market condition dictates what speeds the manufacturer has to produce. For instance, the manufacturer may like to sell 700MHz but all the major system players may be still selling systems at 650MHz. As a result, the manufacturer may be forced to mark down perfectly 700MHz processors as 650MHz.
From the above it is clear that giving the right conditions, a processor can be either down-clocked or over-clocked. An 800MHz processor could run at 700 or 650MHz as long as the motherboard allows. Similarly, it could also run at 900 or even higher.

Why does one need to down-clock a processor? Here is an example. Say, you won a bid for one hundred 600MHz systems. The bid was submitted two months ago. By the time you finish half of the delivery, the 600MHz processors dry out in the market. Now the 650MHz is even cheaper than 600MHz. It would be hard for you to beg Intel or AMD to make another fifty 600MHz processors just for you. On the other hand, the school does not want to change the required specifications mid-stream. Now what do you do? In theory, you can use the 650MHz processors and just clock them at 600MHz!

Of course, most of us would be interested only in overclocking - getting the most juice out of your processors. That gives birth to the overclockers, overclocking community and culture in the past several years.

How to set the clock speed of a processor?

The actual clock speed of a processor is set by the motherboard. There are two ways to do this.
  1. Hardware jumpers. You can change the jumpers to get different combinations of basic BUS speeds and multipliers. Please read the motherboard installation guide for details. This method is used for most brands of motherboards. It is however inconvenient since you need to actually open the case to access the motherboard and

     
  2. Software "jumpers." You change the clock speeds (and often the core voltage, too) of a processor using software embedded in the motherboard BIOS. Most over-clockers like this option. Notable motherboard brands that use software jumpers are Abit and QDI.
How to Do Overclocking?

You need the following to successfully overclock a microprocessor: an overclockable processor, an over-clocking-friendly motherboard, and a plan for a great thermal solutions including heat sink and extra system cooling fans.

This article is only an introduction to the overclocking concept. It's not the intention of this article to teach you exactly how to do overclocking. We suggest you get help from other "overclocking heaven" web sites for more detailed information. We have listed a few of them at the end of this article. Here is a brief guideline:
  • Some processors may be more "overclockable" than the others. If you plan to overclock a processor, choose it carefully. Processors have different stepping codes related to the manufacturing date and conditions. Different stepping codes on the processors of the same speed may present different overclocking opportunities. Both Intel and AMD produce processors that are over-clockable.

     
  • Some motherboards are more overclocking-friendly than the others. Again, choose it carefully. Follow the experience of a successful story. That always helps.

     
  • Once you become an overclocker, you should always try to keep the processor and the entire system cool to ensure stability. Your number one enemy for overclocking is heat (besides your own psychological self). Here are some advises: (1) Add additional system coolers in the front and back of the case to generate an air flow pattern coming in from the front and exiting at the back. (2) Make sure the cooling fans for the power supply sucks hot air out of your system box. (3) Use thermal compound between a good and strong heat sink and the processor to ensure great thermal contact and thus heat dissipation.
What are the benefits?
  1. The increased performance with minimum cost
  2. Self satisfaction from achieving it.
What are the risks?
  1. Overclocking may void the microprocessor warranty since you're using the processor under conditions that are not recommended by the manufacturer. Well, for good reasons, manufacturers certainly do not want any one to overclock.
  2. Overclocking may reduce the life-time of your system. You may want to monitor the temperature of your processor closely.
  3. Overclocking may cause system less stable. If you find your system unstable at higher speeds, just slow it down!


 

Overclocking FAQ (more)