Before we start the actual overclocking process, you should understand that there are two basic strategies for successfully overclocking the processor. These are FSB Overclocking and Multiplier Manipulation. The best results come from the use of both of these techniques together, but you can use either of them individually as well.
It should also be noted that not all motherboards will support overclocking attempts. The main motherboards that will not support this type of setting adjustment are the ones from system vendors like Dell, IBM and Gateway. Though there are a lot more manufacturers who fall into this realm, this will serve to give you an idea of what I am talking about.
And why would a vendor remove the ability to adjust settings like this? Support! When it comes to overclocking, there are many things that can either go wrong, or at least become unstable without proper tweaking. If a manufacturer can remove the ability to adjust speed settings beyond default, then they are effectively reducing the amount of technical support required to service their product line.
Now that we have that out of the way, let's talk turkey.
When it comes to general overclocking, this is probably the most common type of method used. In our definition of FSB we stated that it was nothing more than the data path between the processor and the memory. The speed of this data flow is measured in Megahertz (MHz). All processors have a native FSB speed. Below is a small listing of some of the more common processors and their associated native FSB speeds:
The trick of overclocking comes in when you raise the default FSB speed to a new level. Since the FSB relates to the raw speed of the data flowing along the motherboard's bus, the benefits of this type of overclocking are immediate. To figure a processor's speed, you take the FSB speed and multiply it by the Clock Multiplier of the processor. Below is a simple example of how the FSB tweaking can affect the system speed:
(FSB) 100 * (Multiplier) 10 = 1000MHz Processor Speed
(FSB) 133 * (Multiplier) 10 = 1333MHz Processor Speed
As you can see, the raising of the FSB can make a dramatic difference in your overall system speed. But what about those newer processors that already have a native speed of 133MHz? That is where your entire system comes into play. Since 133MHz FSB is the highest current official FSB speed, you may have to tweak your system a bit to achieve higher overall speeds. We'll talk later on about some of the tweaks that can help you gain higher speeds, but for right now we'll just state that you really can get higher than 133MHz FSB, and in some cases a lot higher.
What we're getting ready to explore right now is the heart of many of the conflicts between the Intel and AMD crowds. When you are able to manipulate the clock multiplier of the processor itself, you are giving yourself a much greater degree of flexibility in your overclocking. But why the big controversy? AMD processors can use multiplier manipulation while Intel processors can't. All Intel processors are locked. What this means is that there is no simple manner to allow the end user the ability to adjust the clock multiplier. AMD processors, on the other hand, while locked from the factory are easily fixed to allow for the adjustment of the clock multiplier. Even better, several motherboard manufacturers put settings right in the system BIOS to make this adjustment a matter of pure ease.
Using the same example as above, by taking the same processor that is now running at 1333MHz, we'll add in a multiplier manipulation and set the clock from 10x to 12x:
(FSB) 133 * (Multiplier) 12 = 1596MHz Processor Speed
As you can see, the difference is once again quite significant. Now just because you have the ability to make the adjustments to FSB and the multiplier does not guarantee a successful overclocking experience. There are several factors to take into consideration. While we aren't quite ready to talk about them all right now, they will be discussed in detail later on.
For Your Consideration
It isn't too hard to find people who will swear by either FSB overclocking or Multiplier Manipulation overclocking. Most who choose one strict discipline over the other are usually newer enthusiasts. Old timers will generally agree that a combination of both of these methods will give you the best results.
Something else to consider is that when you overclock by means of the multiplier, all of the extra power is coming directly from the processor. There is no other component that is helping create a more powerful system. While some may state that this is less stressful to the system components, it goes without saying that when we have help from other components, we should be able to get better results. Here is what I mean:
When you adjust the multiplier, the processor is the only component being stressed. When you raise the FSB to gain higher speeds, the entire system is working together to garner these faster speeds. Why? Because when you raise the FSB, you are also raising the speeds of the AGP, PCI and ISA ports. These ports run at a fixed speed that is computed as a ratio of the FSB. Native speeds are as follows:
A ratio equation is built into every motherboard's chipset to allow for these values when the system runs at default speeds. Since the equation is built in, there are very few methods of bypassing it. With this in mind, it is a simple matter to see why the higher FSB speeds will force these ports to run at faster speeds. This is also where you may start running into bottlenecks since some components will not run well at speeds much higher than default. The most notable bottleneck is the NIC cards, but manufacturers have been striving for better flexibility so even these components are generally better than they once were.
A final thought in this category is your choice of chipset. The newer the chipset, the greater likelihood of a successful overclock. Not only are the newer models allowing for higher FSB speeds, they are also beginning to incorporate additional ratio settings between the FSB and the port speeds. The benefits of these are rather obvious, but the idea of being able to run a 166MHz FSB and still have your ports at their default speeds should be ringing bells in your head right about now.