Overclocking the CPU

Now you know enough to try to overclock your CPU. The step-by-step instructions are simple: increase the FSB frequency in the BIOS, save the settings, boot up the OS and test your PC for stability while keeping your eye on the temperature reading. If you haven’t ever seen a BIOS screen in all your life and can’t find the necessary settings, browse our CPU Overclocking Guide. The frequency can at first be increased with a big enough step like 50MHz or even 100MHz, depending on your CPU model. You should have learned the frequency peak of your CPU and set the frequency accordingly, but the potential of a given sample may differ greatly from the average value. Then, reduce the step to 20, 10 or even 5MHz. Overclocking with a 1MHz precision only makes sense when you are trying to set a new record. For everyday operation, it’s better to have a reserve of stability to safeguard yourself against the natural fluctuation of such characteristic as temperature and voltage.

You go on increasing the frequency while the system is stable and passes all the tests. When errors occur, you reduce the frequency and thus find the limit for your particular CPU.

Can you overclock more? Yes, but you have to increase the voltages for that.

Do you have to increase the voltage?

It’s hard to give a short answer to this question. You should first decide what voltage needs increasing. This is verified through experimenting. Try to increase the CPU voltage by one or two minimum steps in the BIOS and then check out if the CPU can now work at a higher frequency than before the voltage increase. If it can, begin to search for the frequency limit under the new conditions. If it cannot, you’ve increased the wrong voltage.

Besides the core voltage, the mainboard itself can limit further overclocking if you have set a high FSB frequency. Try to increase the voltage on the chipset’s North Bridge a little. Try to change voltages in combination, e.g. increase the FSB termination voltage if your BIOS offers this option. You have fixed all the voltages at their defaults before overclocking, but now you can get a hint from your mainboard: set the voltages to Auto and see what ranges they are changing in.

How high can you increase the voltages? There are three factors that can stop you: the mainboard’s capabilities, a too high temperature, and a lack of purpose. If your system reacts eagerly to a voltage increase and the temperatures remain within normal ranges, why not continue? But if you need to increase your CPU voltage by 0.3V to overclock by 100MHz, I don’t think it makes much sense. The effect from such a small frequency increase won’t be conspicuous for a modern CPU but your system will be put under a stress and the temperature will grow up, too. The CPU temperature increases along with its frequency, but it does so at a much faster rate when you increase the core voltage.

What temperature is normal?

A CPU temperature of 40-50°C is normal. It can grow up to 60°C under load but you should avoid a temperature of 70°C and higher. Replacing the cooler is not the only option to decrease the temperature. If your PC is rather old, you may try to reinstall the cooler and update the thermal grease and the temperature should go down considerably. The temperature will be growing up inevitably in a small and poorly ventilated system case. Installing system fans should help.

Talking about temperatures I mean the CPU temperature in the first place, yet it is not the only one that you should keep your eye on. Keep track of the chipset temperature, especially if you have increased its voltage. The thermal sensor is built into the North Bridge in Intel’s new chipsets. So far there is no program that can monitor this temperature, but such software will surely come out soon.

Mainboards can regularly monitor two temperatures, CPU and system. The system temperature is not the chipset temperature. There is a thermal sensor on the mainboard, usually located near the I/O chip (from Fintek, ITE or Winbond), and its reading is shown as the system temp. Depending on the exact location of the sensor, this temperature may be an important indicator or may be quite useless (and even not changing at all).

Note also the temperature of the MOSFETs near the CPU, especially if you use a liquid cooling system. These usually become very hot under load, but few makers of liquid cooling solutions provide any means to cool them. Memory modules remain almost cold even after a considerably voltage increase but become hot when the memory chips are being accessed intensively.

Do you have to decrease the multiplier?

There is yet another way to increase your system performance. Almost all of modern CPUs allow decreasing the frequency multiplier. You can decrease it and increase the FSB frequency appropriately, keeping the resulting CPU clock rate unchanged. The FSB frequency affects the overall system performance. The higher it is, the faster data flows throughout the PC. Thus, a 3GHz CPU working at a 300MHz FSB with a x10 multiplier will generally be faster than the same 3GHz CPU working at a 200MHz FSB with a x15 multiplier.

This safe and free method of lifting the performance of your system a little more won’t suit everyone, however. The fact is, the power-saving technologies implemented in CPUs stop to work when you change the multiplier because they are themselves based on the reduction of the multiplier and voltage in idle mode. Such technologies play an important role in reducing power consumption and temperature, so this method will only suit people whose PC is loaded all the time, e.g. with distributed computing software. It’s going to be indeed free for them as they get an increase of speed without losing in anything.