Unfortunately, the engineering and manufacture of chips are not exact sciences and it is impossible to know in advance the exact speed at which any particular chip will be able to work. Once a series of processors has been obtained (in principle, all at the same established speed, e.g. 800 Mhz), these chips are tested in a test bed. Those passing the tests at 800 Mhz are labelled as such and put on sale.
Those that don’t pass the test are successively transferred to tests at lower speeds (e.g. 766 or 733 Mhz) and are labelled with the speed of the test they eventually pass. These tests are extremely demanding and, to carry on with the example, we may find a processor on the market originally designed to work at 800 Mhz but labelled at 733, which gives us “ample” room for overclocking.
The level of overclocking of a processor will depend on the specific make and model; some really cannot be pushed any further, or may only be stretched a small amount. Generally speaking, component speed can be increased by an average of 15%, with Intel processors allowing more stretching, whereas AMDs will not allow so much as they invariably work to the fullest of their capabilities.
Before getting down to work, we must first understand how the processor’s speed is reached. At present, the speed of the CPU is determined by two factors: the speed of the clock in the motherboard (whose values affects all the components in the computer) and the frequency multiplier (whose value only affects the processor).
When multiplied by each other, these values configured through the motherboard will determine the speed at which the processor works.
For example, if we imagine a computer that works at 600 Mhz, there are a number of ways of arriving at this figure:
Motherboard bus speed
CPU Multiplier
CPU Speed
133 Mhz
x 4.5
= 600 Mhz.
100 Mhz
x 6
= 600 Mhz.
In our case, the final speed of the processor is the same, but with the first configuration we increase the speed of the motherboard bus, thus raising the performance of all the devices installed in it (BUS, PCI, memories, etc.). Conversely, the second configuration is much more conservative and we do not overstretch any of the components in the computer.
The next step is to check what motherboard and CPU multiplier speed values are being used by the present system configuration and what values it allows. To do this, you need to consult the motherboard manual, which will give all this information in detail, and which will give an idea of the possible combinations. If you do not have the manual, look up the manufacturer’s website, where you will also find all the information.
At present, the speed of the motherboard varies between 66, 75, 83, 100, and 112 Mhz, although other boards have a wider selection: 50, 55, 60, 90, 95, 105, 110, 115, 120, 125, 133 and 150 MHz. This gives even greater flexibility when combining frequencies and, in any case, if your CPU refuses to work at a higher speed, you can always make the bus of the motherboard go faster, even with the CPU working at a similar frequency, and get higher CPU-bus PCI transfer speeds, which will give you an overall increase in the system’s performance.
The two values that determine the speed of the processor (frequency of the bus or clock and multiplier) are found on the motherboard. The method used to change them depends on the model of motherboard itself. There are several ways:
The two values that determine the speed of the processor (frequency of the bus or clock and multiplier) are found on the motherboard. The method used to change them depends on the model of motherboard itself. There are several ways:
Using jumpers or microdips
Both the jumpers and the microdips act as switches which change the configuration of the motherboard and are, logically, located on it, so to change their position you have to open up the computer. Both have two positions: “on” and “off” or “close” and “open”.
The jumpers are small metal pins standing out perpendicularly from the motherboard. If they have a cap on them this means that they are in the “on” or “close” position (circuit closed). If they don’t, then they are “off” or “open” (open circuit).
The microdips serve the same purpose as the jumpers but in a different way. They are like a box with small pins, which may be in either of the two positions described above.
Microdips
Each speed of the motherboard bus and the CPU multipliers has a different position from the jumpers, the colours of which might be black, blue, white, yellow or red, according to the manufacturer.
Once you have assigned the new speed of the motherboard bus using the jumpers, you then modify the CPU multiplier.
The configuration of the CPU multiplier is done in the same way as for the speed of the motherboard bus.
Using BIOS
Recently, there have been many motherboards whose speeds can be configured using Bios, so you don’t have to open up the computer to change the speed, although you should bear in mind that the fact that these parameters are more accessible using BIOS rather than the jumpers does not mean to say that trying multiple combinations is any less harmful. Generally speaking, this option is to be found in the Chipset Features section.
Steps to follow to adjust frequencies using BIOS.
1) Switch on or restart the computer and, during the memory check, detection of hard disks and CPU phase, press the DEL key when the message "Press DEL to enter SETUP” appears on the bottom left-hand side.
2) In the blue computer Setup window (Bios), move onto the Bios Features Setup, CPU Soft Menu or similar option and press Enter.
3) Modify the CPU Host Bus Frequency, Ext. Clock (PCI) or similar option with Page Down until you find the motherboard bus speed you want (e.g. 112 Mhz for processors whose bus normally works at 100 Mhz).
4) In the CPU Core section: Multiple Bus Frequency, Multiplier factor or similar, modify the value of the CPU Multiplier (which can change from 2.0x up to
. 5) Exit Bios saving the changes by pressing the F10 function key and answering the SAVE to CMOS and EXIT (Y/N)? message by pressing Y.
Both
This is a mix of the above types. Some motherboards can be configured both by the jumpers and by bios, the second option being the one offering more configuration possibilities.
This possibility, mentioned in passing, was used a lot in the age of processors with doubled clock speed (i.e. Intel SX and DX processors), now in disuse as it is not particularly advisable, and indeed quite dangerous for the processor.
This consists of increasing the CPU frequency multiplier and then adjusting its power voltage. This way, the pulses of the clock will be a little “stronger” and there is no possibility of losing them or of the processor detecting them after having increased the processor frequency (by the CPU multiplier).
Some boards have a voltage regulation of 2V to 4V (both for the jumpers and for BIOS). The voltage at which the processors work varies according to the make and model, but they range from 2V to 3.3V (except for the Athlons, which work at 1.6V). This means that by raising the voltage gradually you increase the speed (never increase the voltage more than 0.2V). However, we advise against this method as it overstretches two different areas of the computer: voltage and frequency. Each of these factors separately increases the heat produced by the chip, and the sum of both of them could lead to its deterioration.
NB: Overclocking is a technique which requires time to set up. It would be absolutely ridiculous to try and make a 500 Mhz processor work at 800 Mhz, so you should not try out the speed of the motherboard bus or the multiplier at speeds you know beforehand will not work.
To overclock safely and reliably, you should increase the values of the parameters gradually and cautiously, ensuring that both the memory and the PCI devices can withstand such speeds.
Problems
The main problem is that the computer simply may not work. Increasing the speed of a processor is not magic: It may work, it may not. If we push the processor too hard, normally it will refuse to start up, there will be occasional crashes or some programs will not work, etc. Besides this, when it does work the first time, problems may arise later with the processor owing to three features of the electronic circuits:
1 Increase in heat: on raising the operating speed, we increase the amount of electricity flowing through the circuit and, consequently, the heat it gives off. This can cause faults or even permanent defects in the chip if the heat is excessive
2 Electromigration: This is a rather ambiguous concept. We know that faster operating speeds cause a kind of ‘erosion’ in the processor’s circuits. This erosion may in time create defects while, evidently, making a processor work at a higher frequency may greatly accelerate this process. It is not clear, however, whether this process is decisive in the (short) life of a microprocessor.
3 A change in the overall configuration of the machine: Stretching the frequency of the processor in many cases involves increasing the frequency of other components: memory, motherboard, video card, etc.
4 Machine guarantee: Overclocking the processor or changing the factory configuration of any of its internal components implies the automatic loss of guarantee.
As a result, it should be remembered that it is possible to seriously damage the computer by making it work beyond its capabilities.
Heat is one of the principal enemies of any electrical equipment, so you should always try to reduce it as much as possible in your system. There are ways of increasing heat dissipation, but they require know-how, money and, on occasions, imagination.
In the first place, you should cool the processor component in question, although the graphics card may also get quite hot. To do this, there is a heat dissipater on the processor that absorbs heat on its surface and expels it, helped by a fan to avoid the hot air accumulating around the processor. The larger the dissipater and the fan, the better.
There are fans that allow the rotation speed or the temperature of the dissipater it is in contact with to be controlled, and this is extremely important.
Other devices, which may help a lot when overclocking, are Peltier cells. These curious contraptions are sheets which, when electrical current passes through them, go cold on one side and hot on the other (which still makes it necessary to have a dissipater and fan on this side). These devices are very efficient but also very expensive, they consume a lot of electricity and they are hard to find. Generally speaking, you have to find sites on the Internet (such as http://www.3dfxcool.com or http://www.computernerd.com) to get hold of them at a good price along with a range of accessories: heat-conducting resins so that the processor and the dissipater make good contact, fans for graphics cards, fans for the hard disk, etc.
In any case, none of this will do any good if you don’t eliminate the heat out from the computer casing. You should bear in mind that the dissipater and the fan do not make the heat disappear, they simply move it around, and it is just as harmful close to the processor as it is accumulated inside the casing without being able to get out.
For cooling to be perfect, the best thing is to have one fan that brings cold air in and another to expel it. In a normal machine, the power supply usually gets rid of the hot air, but there is not usually an entry fan, so it would be a good idea to buy a fan and install it in the front part of the computer, where there are normally holes ready to take an 8x8 cm fan.
In any case, there are two things you should not forget: 1) hot air rises, so the air vent should be up high (NEVER below the cold air vent); 2) there are few ventilation systems as effective and as cheap as opening the computer casing. It doesn’t look very pretty (although this is just a matter of taste) but it does work very well.
You should remember that by increasing the frequency of the clock you also increase energy consumption, and that by adding fans we may be exceeding the power supply limit .
