How greatly shall we raise it? I don’t know the answer to this question. A lot depends on your CPU, mainboard, cooling system and power supply unit. Start little by little: try raising the FSB frequency by 10MHz above the nominal – it should work just fine in most cases. Don’t forget to save the changes, load the Windows, make sure that the CPU really did overclock (you can use something like a CPU-Z utility to check this out). After that check how stable your system is by running some program (like Super PI, Prime95, S&M) or game. Of course, you have to make sure that this program runs stable on your system before you undertake any overclocking attempts. And do not forget to monitor the CPU temperature: the lower it is – the better, and make sure that it doesn’t exceed 60o C.
If you have an Intel Pentium 4 or Celeron CPU, you should use ThrottleWatch, RightMark CPU Clock Utility or something like that. The thing is that these processors could start throttling in case they get overheated thus reducing the system performance dramatically. It doesn’t make any sense to undertake any overclocking experiments in case the CPU is “throttling”, because the performance may drop even below the level achieved with the nominal settings. These utilities will report if throttling occurs, so that you could improve the CPU cooling or take it easier on overclocked settings.
If everything came out OK, you can increase the FSB frequency a little bit more until the system remains stable. Once you start noticing the first signs of over-overclocking, such as freezing, unexpected program termination, error messages, blue screens, or once the temperature grow too high, you have to get back to the lower FSB value and make sure the system remains stable in this case again.
Very often you may refer to our previous overclocking related articles to evaluate how far your CPU can approximately go. Just be attentive and keep in mind that it is not only the CPU name that matters, but also the type of the core it is based on and even the core revision. Moreover, even the CPUs from one and the same supply can have different overclocking potential, so don’t try to immediately set the maximum frequency you have even seen mentioned in relation to the same CPU: it would be much safer for you and for your system to reach these heights step by step.
However, there can also be exceptions. Remember, when I mentioned the older chipsets that cannot lock the AGP and PCI frequencies at their nominal values? It is true, they cannot support the nominal frequencies of these busses throughout the entire FSB frequency range. But they have to keep these frequencies at nominal when the CPUs work at their standard clock rates. This is done with special dividers that switch automatically depending on the FSB frequency. The standard frequencies in this case are: 100, 133, 166 and 200MHz.
Suppose that we overclocked a Duron processor from 100MHz to 120MHz on the bus and it remained absolutely stable all the time. But when we increased the FSB frequency to 125MHz, some freaky things started happening and the system would even refuse to boot at all. Of course, we could have reached the top of the CPU overclocking potential, but it could be a completely different reason. What if the CPU can go much farther than that, and it is the higher AGP and PCI bus frequencies that do not let us continue? You can check it out pretty easily: set the frequency to 133MHz. In this case the mainboard will use different dividers to set the bus frequencies to their nominal values. If your CPU copes with this overclocking, you will be able to go somewhat higher.