|
The Basics of Overclocking
(A continuation to "What is Overclocking")
The Basics
To understand how to overclock your system, you must first understand how your system works. The most common component to overclock is your processor.
When you buy a processor, or CPU, you will see it's operating speed. For instance, a AMD 2500+ CPU runs at 1.83GHz, or 1830 MHz. This is a measurement of how many clock cycles the processor goes through in one second. A clock cycle is a period of time in which a processor can carry out a given amount of instructions. So, logically, the more clock cycles a processor can execute in one second, the faster it can process information and the faster your system will run. One MHz is one million clock cycles per second, so a 1.8GHz processor can go through 1,800,000,000, or 1 billion eight hundred million clock cycles in every second. (AMAZING)
The goal of overclocking is to raise the GHz rating of your processor so that it can go through more clock cycles every second. The formula for the speed of your processor if this:
FSB (in MHz) x Multiplier=Speed in MHz.
Now to explain what the FSB and Multiplier are:
The FSB (or, for AMD processors, the HTT*), or Front Side Bus, is the channel through which your entire system communicates with your CPU. So, obviously, the faster your FSB can run, the faster your entire system can run.
CPU manufacturers have found ways to increase the effective speed of the FSB of a CPU. They simply send more instructions in every clock cycle. So instead of sending one instruction every one clock cycle, CPU manufacturers have found ways to send two instructions per clock cycle (AMD CPUs) or even four instructions per clock cycle (Intel CPUs). So, when you look at a CPU and see it's FSB speed, you must realize that it is not really running at that speed. Intel CPUs are "quad pumped", meaning they send 4 instructions per clock cycle. This means that if you see an FSB of 800MHz, the underlying FSB speed is really only 200MHz, but it is sending 4 instructions per clock cycle so it achieves an effective speed of 800MHz. The same logic can be applied to AMD CPUs, but they are only "double pumped", meaning they only send 2 instructions per clock cycle. So an FSB of 400MHz on an AMD CPU is comprised of an underlying 200MHz FSB sending 2 instructions per clock cycle.
This is important because when you are overclocking, you will be dealing with the real FSB speed of the CPU, not the effective CPU speed.
The multiplier portion of the speed equation is nothing more than a number that, when multiplied by the FSB speed, will give you the total speed of the processor. For instance, if you have a CPU that has a 200MHz FSB (real FSB speed, before it is double or quad pumped) and has a multiplier of 10, then the equation becomes:
(FSB) 200MHz x (Multiplier) 10= 2000MHz CPU speed, or 2.0GHz.
On some CPUs, such as the Intel processors since 1998, the multiplier is locked and cannot be changed. On others, such as the AMD Athlon 64 processors, the multiplier is "top locked", which means that you can change the multiplier to a lower number but cannot raise it higher than it was originally. On other CPUs, the multiplier is completely unlocked, meaning you can change it to any number that you wish. This type of CPU is an overclockers dream, since you can overclock the CPU simply by raising the multiplier, but is very uncommon nowadays.
It is much easier to raise or lower the multiplier on a CPU than the FSB. This is because, unlike the FSB, the multiplier only effects the CPU speed. When you change the FSB, you are really changing the speed at which every single component of your computer communicates with your CPU. This, in effect, is overclocking all of the other components of your system. This can bring about all sorts of problems when other components that you don't intend to overclock are pushed too far and fail to work. Once you understand how overclocking works, though, you will know how to prevent these issues.
*On AMD Athlon 64 CPUs, the term FSB is really a misnomer. There is no FSB, per se. The FSB is integrated into the chip. This allows the FSB to communicate with the CPU much faster than Intel's standard FSB method. It also can cause some confusion, since the FSB on an Athlon 64 can sometimes be referred to as the HTT. If you see somebody talking about raising the HTT on an Athlon 64 CPU and is talking about speeds that you recognize as common FSB speeds, then just think of the HTT as the FSB. For the most part, they function in the same way and can be treated the same and thinking of the HTT as the FSB can eliminate some possible confusion.
How to Overclock
Well, the most common method of overclocking is through the BIOS. The BIOS can be reached by pressing a variety of keys while your system is booting up. The most common key to get into the BIOS is the Delete key, but others may be used such as F1, F2, any other F button, Enter, and some others. Before your system starts loading Windows (or whatever OS you have), it should have a screen that will tell you what button to use at the bottom.
Once you are in the BIOS, assuming that you have a BIOS that supports overclocking*, you should have access to all of the settings needed to overclock your system. The settings that you will most likely be adjusting are:
Multiplier, FSB, RAM Timings, RAM Speed, and RAM Ratio.
On a very basic level, all you are trying to do is to get the highest FSB x Multiplier formula that you can achieve. The easiest way to do this is to just raise the multiplier, but that will not work on most processors since the multiplier is locked. The next method is to simply raise the FSB. This is pretty self explanatory, and all of the RAM issues that have to be dealt with when raising the FSB will be explained below. Once you've found the speed at which the CPU won't go any faster, you have one more option.
If you really want to push your system to the limit, you can try lowering the multiplier in order to raise the FSB even higher. In order to understand this, imagine that you have a 2.0GHz processor that has a 200MHz FSB and a 10x multiplier. So 200MHz x 10=2.0GHz. Obviously, that equation works, but there are other ways to get to 2.0GHz. You could raise the multiplier to 20 and lower the FSB to 100MHz, or you could raise the FSB to 250MHz and lower the multiplier to 8. Both of those combinations would give you the same 2.0GHz that you started out with. So both of those combinations should give you the same system performance, right?
Wrong. Since the FSB is the channel through which your system communicates with your processor, you want it to be as high as possible. So if you lowered the FSB to 100MHz and raised the multiplier to 20, you would still have a clock speed of 2.0GHz, but the rest of the system would be communicating with your processor much slower than before resulting in a loss in system performance.
Ideally, you would want to lower the multiplier in order to raise the FSB as high as possible. In principle, this sounds easy, but it gets complicated when you involve the rest of the system, since the rest of the system is dependent on the FSB as well, chiefly the RAM.
*Most retail computer manufacturers use motherboards and BIOSes that do not support overclocking. You won't be able to access the settings you need from the BIOS.
Courtesy of Tazz1964
|
