Introduction to Overclocking

Overclocking is the technique used to increase the speed of a device beyond stock. ‘Stock' is the name given to the default specifications of a device. Once you have altered the device it is no longer considered stock unless it is returned to its initial specifications. Overclocking describes the alteration of clock speed above stock (hence the name overclocking) of any given device, usually RAM and CPUs, but also other components such as GPUs and PCI busses. When a devices clock speed is decreased from stock (or from an overclock), it is called underclocking.

WARNING: It is human nature to blame someone else if something goes wrong. This is where I warn you, the reader of this article, that neither the author nor this website recommend that you overclock your computer hardware. This article explains how the author conducted these experiments on his own property. Benchmarkreviews.com and the author of this article will not be responsible for damages or injury resulting from experiments you choose to conduct on your own property. If you read beyond this point, you are accepting responsibility for your own actions and hold the Benchmark Reviews website and the staff of benchmarkreviews.com harmless.

NOTE: Not all hardware can be overclocked. Research the components you wish to overclock using a search engine such as Google, and check if they are capable of being overclocked. Searching the model number of your motherboard along with "overclock" should help you determine whether the system is capable. If in doubt, ask here.

Dangers of Overclocking

Overclocking is safe. There, I said it. I will not attempt to scare you away from overclocking. I believe that if you learn properly you can overclock without trouble, as long as you know your limits. This tutorial explains how to determine these limits. I am not liable if you damage anything by following this tutorial. Overclock at your own risk. Please note that overclocking can decrease the lifespan of your components. You are welcome to ask me any questions here.

Overclocking and Warranty

Before you leap into the world of overclocking, check that you aren't voiding your warranty. Most devices will forfeit your warranty when overclocking is performed, so the main rule of thumb is to not overclock anything you cannot afford to replace. Even though overclocking is fairly safe to perform, it is not very smart to risk breaking something if you cannot replace it.

What Determines CPU Performance?

The performance of a CPU is determined by its frequency (or clock speed), architecture and cache.
The architecture of CPUs is constantly evolving, and with this we get faster processors that run cooler and more efficiently. Multiple core CPUs are a prime example of architecture improvement. Two or more cores allow data to be processed more efficiently therefore increasing performance, sometimes even with smaller clock speeds. The performance difference between single and multiple core CPUs is dependent on the software and OS you are running. With overclocking we can't change architecture because it is a physical component. The only way to alter architecture is to buy a new CPU altogether.

Clock speed is the rate in which data is processed. It is common for people to get confused with this idea and assume that a bigger clock speed CPU runs faster than a lower clocked CPU. This is not necessarily true, especially when there is a major architecture difference. An interesting comparison of CPUs at the same clock speed but with different architectures can be found here.

If you were to compare two identical CPU models, each with different clock speeds, the higher clocked CPU would be the faster processor.

Why should I overclock?

Overclocking is performed for many reasons including:

The Need for More Performance

There comes a time when your PC no longer has the grunt to run software comfortably due to lack of performance. Older or low end PCs suffer this problem when a demanding piece of software is installed. It is important to locate what the problem is before resorting to overclocking. The problem may well be lack of RAM, which overclocking cannot fix.

To Relieve a Bottleneck

Bottlenecking is the term used to describe a component in your PC which is restricting other components due to lack of performance or efficiency. Overclocking can relieve a bottleneck if the problem lies with the CPU, RAM or GPU clock speeds. Bottlenecking is impossible to overcome completely, but it can be minimised with careful planning. Remember that a PC is as fast as its slowest component.

To Exercise a Known Safe Clock Speed

Some low to mid-end devices are underclocked versions of higher-end models. These lower-end models can then be overclocked by the end user to get similar (or possibly better) performance than the higher-end models. This is common with CPUs which use a binning process to determine what clocks CPUs get. This is great for the consumer because it allows us to spend less and then overclock to get significantly higher speeds. Some of these lower-end models have a safe known clock speed which they can perform stably on stock voltages. Voltages and stability will be discussed further on in the tutorial.

For Fun, Hobby or Competitive Reasons

Some people enjoy getting the most out of their system without spending a cent. Others spend money on complex cooling setups such as water cooling and vapor phase change units. Cooling is important when overclocking and will be discussed later in the tutorial. Overclocking competitions are becoming popular and allow skilled overclockers to showcase their talent.

To Learn More About your System

Overclocking allows you to understand how components communicate and function. It also allows you to learn what some of those jargon words mean such as DDR (double data rate).

Overclocking Theory: Intel

Overclocking depends on several factors. Cooling, voltage, architecture, and hardware limits all determine how much a device can overclock.

NOTE: Before attempting an overclock, I advise that you read the entire tutorial first. Remember that this is the ‘Theory' section, so be sure to also read through the ‘Practical' section.

What is a ‘clock cycle'?

A ‘clock cycle' is the time it takes for an instruction to be processed by a device. These devices are measured in Hz (e.g. MHz or GHz) which describe how many clock cycles are performed per second. For example, a 3GHz processor performs 3,000,000,000 clock cycles per second.

Intel CPUs

Intel CPUs are overclocked via the FSB (Front Side Bus) and CPU multiplier. The FSB controls the communication between the CPU, RAM and PCI busses. There are two types of FSB; one determined by the CPU called the ‘Rated FSB' and the other is the ‘Bus Speed'. ‘Bus Speed' is what is used to calculate clock speed. When you hear/read people referring to FSB, it is most likely referring to the Bus Speed. ‘Rated FSB' (or ‘effective FSB') is a little more confusing. Rated FSB is the name given to the result of the Bus Speed when a CPU uses double or quad pumping. Double pumping is double the Bus Speed and Quad Pumping is four times the Bus Speed.

What is ‘pumping'?

When an Intel CPU is double or quad pumped, it means that the Bus Speed is effectively doubled or quadrupled. It does NOT do this by increasing the actual Bus Speed, but instead sends more data per clock cycle. In other words, for every clock cycle in a quad pumped CPU, it sends and receives four times the data.

NOTE: Overclocking PCI busses is not recommended as it can easily cause system instability. Most motherboards lock the PCI bus so it cannot be altered.

The ‘multiplier‘ is a number which is multiplied by the Bus Speed to determine the CPU clock speed. The multiplier is often locked, meaning it cannot be changed. Sometimes the multiplier is partly locked, which only allows a smaller number, or completely unlocked (quite rare these days).

Let's examine a practical example:

Let's say the Bus Speed of a computer is 300MHz and the CPU multiplier is 11x. To determine the clock speed that the CPU is running at, we multiply the FSB by the multiplier.

11 (Multiplier) x 300 (Bus Speed) = 3300MHz (3.3GHz)

However, Intel CPUs from Pentium 4 upwards are ‘quad pumped'. This means that the 300MHz Bus Speed is effectively running at 1200MHz. This, however, does not affect overclocking. When adjusting values we are only adjusting the Bus Speed.

For example:

Let's say the Bus Speed is 300MHz and has a quad pumped CPU with a multiplier of 11x.

300MHz (Bus Speed) x 11 (Multiplier) = 3300MHz (3.3GHz) - Note how this is the same as the above example.

If we were to do the same calculation but with the Rated FSB, it would look like this:

1200 (Rated Speed) x 11 (Multiplier) = 3300MHz (3.3GHz)

It's the same result because you must divide the Rated FSB by 4 (since it's quad pumped). Clock speeds are only calculated with the Bus Speed, not Rated FSB.

Some Intel CPUs are double pumped. This uses the same concept as quad pumping but you multiply the Bus Speed by 2 instead.

For example:

Let's say the FSB is 300MHz and has a double pumped CPU with a multiplier of 11x.

300MHz (Bus Speed) x 11 (Multiplier) = 3300MHz (3.3GHz)

The Rated FSB is 600MHz. So,

600MHz (Rated FSB) x 11 (Multiplier) = 3300MHz (3.3GHz) because it's double pumped.

You're probably thinking right now, "Why do I need to know about the Rated FSB if I never use it?" Truth be told, you don't. It does help, however, when looking at Intel's specifications for their CPUs. Intel often advertises their CPU FSB speeds in Rated FSB instead of Bus Speed. So knowing how to find the Bus Speed from this data can help.

Overclocking Theory: AMD CPU's

Although the technology used in AMD CPUs differ from Intel processors, the technique for overclocking is still very similar. The main difference is that there is another factor to consider called the LDT Bus. This separate bus allows communication between the CPU and the motherboard chipset.

The Technique Behind HyperTransport

HyperTransport can be considered as AMD's version of the FSB. All AMD CPUs with HyperTransport are treated as ‘double pumped'. With Intel CPUs, the FSB is on the motherboard, but with AMD CPUs, the FSB is on the actual CPU. The Bus Speed is called the ‘HT Bus' when working with AMD processors. There are two busses in an AMD CPU, the LDT Bus (Lightning Data Transport) which communicates with the motherboard chipset, and the HT Bus which communicates with the RAM and determines the clock speed of the CPU. The LDT Bus is sometimes known as the ‘HT Link'. The LDT Bus Speed is derived from the HT Bus and ‘HT Multiplier'. Confusing? Here are some examples:

Let's say the HT Bus is 200MHz, the multiplier is 11x, and the HT multiplier is 5x for an AMD CPU.

To find the LDT Bus frequency we find the product of the HT multiplier and the HT Bus:

200 (HT Bus) x 5 (HT Multiplier) = 1000MHz (LDT Bus)

To find the clock speed of the CPU we find the product of the HT Bus and the CPU multiplier:

200 (HT Bus) x 11 (CPU Multiplier) = 2200MHz (2.2GHz)

As you can see, the method is similar to Intel CPUs except with the addition of the LDT Bus.

The Technique Behind the LDT Bus

The trick with the LDT Bus is to keep it as close to stock as possible. Most CPUs come with a stock HT Multiplier of 5x when the HT Bus is 200MHz (200 x 5 = 1000MHz). Essentially, you should try and keep the LDT around 1GHz as most motherboards do not allow too much overclocking of this bus. When overclocking, the HT Multiplier may have to be lowered to 4x so that the HT Bus can be raised without making the LDT Bus unstable. 1100MHz is the maximum frequency the LDT Bus should reach before dropping the HT multiplier (this can vary depending of the model of motherboard). Because the LDT Bus communicates with other busses such as PCI, SATA, USB, it is essential that they are locked to prevent instability. Most modern motherboards lock these busses automatically. For example:

Let's say you want to get you HT Bus to 250MHz so your CPU with 11x multiplier can reach 2.75GHz. If the HT Multiplier is set to 5x, the result will be the following:

CPU clock speed: 250 (HT Bus) x 11 (CPU Multiplier) = 2750MHz (2.75GHz)
LDT Bus: 250 (HT Bus) x 5 (HT Multiplier) = 1250MHz (1.25GHz)

Notice how the LDT Bus is set too high. To fix this, just lower the HT Multiplier:

LDT Bus: 250 (HT Bus) x 4 (HT Multiplier) = 1000MHz (1GHz)

This result is much better. If you are overclocking and over the limit for the LDT Bus, yet lowering the HT Multiplier results in a frequency lower than stock, you have two options. Either do a stress test (explained later in the tutorial) with the higher HT Multiplier and check if it's stable, or lower the HT Multiplier anyway. Underclocking the LDT Bus is not as bad as it sounds, as long as it stays close to 1GHz. Further HT Bus overclocking will bump the LDT up anyway.

For example, let's say the same CPU is using a HT Bus of 225MHz instead:

LDT Bus: 225 (HT Bus) x 5 (HT Multiplier) = 1125MHz (1.125GHz)

This is just above the LDT Bus recommended limit, so you can either stress test it to check stability, or lower the HT multiplier:

LDT Bus: 225 (HT Bus) x 4 (HT Multiplier) = 900MHz

900MHz is still efficient enough for the CPU to run without a bottleneck, but if stable, the 5x HT Multiplier is recommended. How to determine stability will be discussed later.

NOTE: The LDT Bus is often called the HT Link. Keep this in mind when overclocking and researching information.

The Technique Behind DDR RAM}

Overclocking RAM is easier to perform than overclocking a CPU. DDR RAM (Double Data Rate Random Access Memory) clock speed can be determined by doubling the FSB/Bus Speed. DDR models include DDR1, DDR2, and DDR3. All models share the same overclocking method.

For example:

Let's say the Bus Speed is 300MHz.

300 (Bus Speed) x 2 (DDR) = 600MHz

It's really that simple.

What is Stability?

Stability is the term that describes a devices ability to perform tasks without error or failure. When overclocking, stability is crucial because an unstable machine is useless. Instability occurs when the clock speed is set too high, or the voltage is set too low. It is generally not a permanent fault. If your system becomes unstable, lowering the clock speed a little or increasing the voltage should fix the problem. Permanent instability can occur if the device is overclocked too far without adequate testing. Testing methods will be outlined further on in the tutorial.

Breaking the Bottleneck Limit

Both RAM and CPUs use the same FSB to overclock. Unfortunately, most of the time the RAM and CPU have different limits, so adjusting the FSB may bring the RAM to its stable limit before the CPU even breaks a sweat.

NOTE: For all the below examples, the stock speed of the CPU is 2.6GHz and stock speed of the DDR2 RAM is 667MHz.

For example:

Let's say the DDR RAM we're using cannot overclock higher than 800MHz without being unstable. The FSB is 400MHz and the CPU is running with a multiplier of 9.

RAM: 400 (Bus Speed) x 2 (DDR) = 800MHz
CPU: 400 (Bus Speed) x 9 (Multiplier) = 3.6GHz

If we were to increase the Bus Speed by 10MHz to further overclock the CPU...

RAM: 410 x 2 = 820MHz
CPU: 410 x 9 = 3690MHz

Now there's a problem! The RAM is unstable past 800MHz, yet the FSB is 410 which makes it 820MHz! But we still want the CPU to overclock further. How can we solve this? By using multipliers (if available) or dividers.

The Multiplier

Adjusting the multiplier is a matter of increasing or decreasing the number. Keep in mind that most CPUs have multiplier locks (as discussed above). If you are lucky enough to have an unlocked multiplier, then tweaking your overclock becomes much easier. Using the example above, we will try to overclock again using multipliers:

RAM: 400 x 2 = 800MHz
CPU: 400 x 10 = 4000MHz (4GHz)

As you can see, by increasing the multiplier by one we are able to get the CPU to 4GHz without touching the speed of the RAM. But there is one problem, in this case, for every one digit increase there is a 400MHz boost. It is inadvisable to do this unless you know that exact CPU can handle it. How can we find out safely? By using dividers.

The Divider

The divider, also known as the ‘RAM Ratio' or ‘RAM:FSB', is a little trickier to use. The divider is a ratio which determines the Bus Speed that the RAM uses. In other words, it alters the communication speed between RAM and FSB. The default ratio is 1:1. This is the ratio that all the above examples used, in other words, both RAM and CPU worked off the same Bus Speed.

AMD's Notation for Dividers

AMD do not use ‘ratios' to depict their dividers. Instead, a 1:1 ratio is said to be ‘200MHz', a 6:5 ratio is ‘166MHz' and so on. Some motherboards show both methods when tweaking to make it easier to understand. The following examples about dividers will be in actual ratio form.

DDR RAM Overclock Details

To help explain how these ratios/dividers work, here is an example of a 1:2 ratio:

Firstly, imagine 1:2 as ½, so:

RAM (with 1:2 divider): 400MHz (Bus Speed) x ½ (divider) x 2 (DDR) = 400MHz
RAM (without divider): 400MHz (Bus Speed) x 2 (DDR) = 800MHz
CPU (with 1:2 divider): 400MHz (Bus Speed) x 9 (Multiplier) = 3600MHz
CPU (without divider): 400MHz (Bus Speed) x 9 (Multiplier) = 3600MHz

NOTE: Remember that the HT Bus (AMD systems only) is equivalent to the Bus Speed in Intel systems. Substitute the terms if using an AMD setup.

As you can see, when the 1:2 divider is on, the RAM speed is halved while the CPU speed stays the same. The divider does not affect the CPU, only the RAM. That particular divider isn't too much use for this example because the RAM becomes severely underclocked.

Let's assume that we know that the CPU can perform 3.6GHz safely (with a multiplier of 9) and the limit for the RAM is 800MHz (RAM stock speed is 667MHz and CPU stock is 2.6GHz). How can we achieve this optimally while allowing for further overclocking? Well using basic maths, 9 x what gives us roughly 3.6GHz? A 400MHz FSB does, so:

RAM: 400 x 2 = 800MHz
CPU: 400 x 9 = 3600MHz

To fix the problem with the limited RAM we can use a 5:6 (â…š) divider:

RAM: 400 x â…š x 2 = 667MHz
CPU: 400 x 9 = 3600MHz

Now the RAM is at stock but the CPU is overclocked to 3.6GHz. Because we don't know the limit of the CPU, we can keep going until it is unstable (reaches its limit). Now the RAM still has quite a bit of headroom to allow the CPU to be pushed further without reaching its limit.

Let's say that after vigorous testing we get the CPU to 4GHz:

RAM: 444MHz x â…š x 2 = 740MHz
CPU: 444MHz x 9 = 3996MHz ~ 4GHz

This is where tweaking comes in. If the multiplier of this CPU is unlocked, we can do the following instead:

RAM: 400MHz x 2 = 800MHz
CPU: 400 x 10 = 4000MHz (4GHz)

Now both the RAM and CPU are performing at their optimum speed. Now you're probably thinking "Why didn't I just increase the multiplier in the first place?!" That's because you didn't know that CPU could handle 4GHz (see the multiplier section above which uses the same example). With the RAM dividers you were able to slowly see what the CPU limit was without jumping from 3.6GHz straight to 4GHz. The CPU could have reached its limit at 3.8GHz, so the multiplier alteration would not help find a stable clock.

Determining the Limit of the CPU & RAM - Stability

With all this talk about device limits and instability, you should be wondering "How the heck did you figure out the ‘limits'?" or "How do I know the PC is unstable? And how do I test if it is?"

The limit of a CPU is determined when you overclock it and it gets to a point where it becomes unstable. Voltage increases will to an extent allow further overclocking, but when this does not help anymore the true limit is reached.

To determine system stability, programs like Orthos Prime & OCCT are used. Orthos Prime stresses both CPU and RAM to see if they are stable. If Orthos Prime can run a couple of hours without the PC freezing, rebooting, or Orthos complaining, then the PC is considered stable. While the stress test is running, it is good to keep track of the temperature. Running software such as Core Temp in the taskbar allows you to monitor CPU temperatures. Remember, anything over 60oC for a CPU is not recommended, and 70oC+ is getting a little dangerous. OCCT works the same way as Orthos, but it is generally more up-to-date. OCCT can be downloaded here, while Orthos Prime can be obtained here.

Pushing it Further - Voltage Increase

The above examples do not consider voltage alterations. In reality, you will not get a 2.6GHz CPU to 4GHz with stock voltage. CPU voltage is called ‘VCore'. RAM voltage is called ‘VDimm' or ‘VDDR'. Increasing voltage allows for higher stable clock speeds, but also causes the component to get hotter. It is advised that the temperature stays under 60oC when under stress.

Always start overclocking with stock voltage if you're using the stock cooler. Gradually overclock the CPU/RAM until you it becomes unstable, and then try a small voltage increase (.25v at a time). More information on how to perform this will be presented in the ‘Practical' section. Make sure you research the CPU and RAM model you're overclocking to see what other people are getting with similar systems. This allows you to plan your overclock and minimise risk of causing damage. Try not to increase the voltage too much. If a voltage increase reaps minimal benefits, it is likely that you have reached the limit of the component or your motherboard.

Other components which can benefit from a voltage increase include the FSB (Bus Speed) or the LDT Bus/HT Link. The voltage of these components should be only adjusted if raising the bus to high speeds such as 400MHz+ causes instability.

Power Requirements

Overclocking with voltage increases puts more strain on the PSU (Power Supply Unit). This is typically not a much of a problem, but if the PSU is already under heavy load a voltage increase could cause problems. The simple solution is to buy a better PSU if problems occur. The main symptoms of PSU overload include random restarting and the PC not powering up properly. It sometimes becomes hard to distinguish between CPU/RAM instability and PSU overload, although most of the time it's the former. If you are unsure, underclock the CPU/RAM to a known stable configuration (but with the voltages still overclocked) and then restart. If symptoms persist, then the PSU is most likely at fault.

Cooling

As soon as you start turning up the voltage in a device, more heat is generated. Some stock cooling can handle a voltage increase and still keep the system relativity cool. When the heat gets too much (over 60oC when under when stress), an aftermarket cooler is recommended. The main issue with aftermarket cooling is that it often voids warranty. This isn't much of a problem since overclocking in the first place usually voids warranty anyway. If you are unsure about aftermarket cooling voiding warranty, check the documentation that came with your components or go to the manufacturer's website. If there is no information, assume that it does void your warranty.

The two main types of cooling are air and water. More extreme cooling techniques use liquid nitrogen and vapor phase change devices, but these setups are expensive. Air cooling is the cheapest solution, but is often the least effective. At the time of me writing this, the ‘Thermalright Ultra 120 eXtreme' is arguably the best air cooled heatsink available. Water cooling on the other hand is harder so setup and commonly costs more than the air method. A good water cooling kit cools a system better than air, but requires more power and space. Water is recommended if fairly intensive overclocking is necessary, otherwise air cooling is better for those on a budget.

The best free way to improve cooling it to clean the dust out of your CPU heatsink. Do this before you attempt an overclock. Benchmark Reviews constantly tests the Best CPU Cooler Performance and offers perspective on the products worth your time and money.

Escape Plan - CMOS Reset

There may come a time where an overclock goes horribly wrong and you cannot access the BIOS to change settings. In this case, a CMOS reset is in order to wipe the saved settings and start from scratch. To do this, open your PC and remove the CMOS battery (the round coin shaped battery) from the motherboard. Take care not to damage the motherboard while removing it, and discharge any static on your body by grounding yourself. Leave the battery out for about a minute then replace it. Some motherboards use ‘jumpers' to reset the BIOS/CMOS so check your motherboard manual before attempting to take the battery out.

Not all Hardware is Equal

Some motherboard, CPU, and RAM models allow for better overclocking than others. If you intend to overclock when buying a new system, do some research for components that are known to overclock well. People often focus on the CPU and RAM, but the motherboard dictates how high the FSB can be increased. Reviews and benchmarks are the best way to determine what components are better for overclocking. A Google search can obtain useful results.

Getting Access to Hidden BIOS Settings

Some BIOSs hide advanced settings and can only be accessed after a certain key combination is pressed. Check your motherboard manual or do a search on Google to find out what combination to use (if applicable). An example is ‘Ctrl+F1' which is commonly used with Gigabyte motherboards. The hotkey should be performed while in the BIOS menu.

Overclocking - Practical

Overclocking can be performed via Windows or through the BIOS. Overclocking via Windows makes it easier to test configurations and stress test without having to restart the PC. The problem with overclocking through Windows is that the settings aren't permanent, so the overclock will only kick in after you boot into Windows.

Overclocking via the BIOS is much more permanent. Settings can be reset if need be via a CMOS reset. Overclocking via the BIOS takes longer to do because after each tweak you must boot into Windows to stress test the CPU/RAM.

Universal Overclocking Tools (for both methods):

Orthos Prime 2004 [Download - Freeware]
Used to stress the CPU and RAM so it is easier to detect instability.

OCCT [Download - Freeware]
Used to stress the CPU and RAM so it is easier to detect instability.

Core Temp [Download - Freeware]
Used to monitor the temperature of Intel Core 2 Duo and AM2 CPUs when idle or under stress.

SpeedFan [Download - Freeware]
Used to monitor the temperature of CPUs when idle or under stress.

CPU-Z [Download - Freeware]
Allows you to check the voltage, Bus Speed, multiplier etc. that you are currently running.

SuperPI Mod [Download - Freeware]
Can be used to check stability, speed and accuracy of a CPU when calculating the number Pi.

NOTE: You may want to print this tutorial to help you while not in Windows.

Overclocking the CPU and RAM via Windows

Specialized Tools:

CrystalCPUID [Download - Freeware]
Used to alter VCore and CPU Multipliers.

ClockGen [Download - Freeware]
Used to alter Bus Speed/HT Bus and PCI-e frequencies.

SetFSB [Download - Freeware]
Used to alter FSB (Bus Speed/HT Bus) and PCI-e frequencies.

Overclocking via Windows is the best way for beginners to try overclocking without the daunting BIOS interface. The great thing is that the settings only take effect while in Windows, so instability can be fixed quite easily.

NOTE: These programs cannot change the HT Multiplier (AMD systems) or RAM dividers, so these will have to be performed via the BIOS if required.

Overclocking the CPU and RAM

The first thing to do is research the components you want to overclock using a search engine such as Google. For example, if you are overclocking an E4300 CPU, go to Google and type "E4300 overclock" and see if you can find a safe known overclock that you can aim to achieve. Also research safe voltages and compare your results to other people. Remember that some hardware is better than others, so if you cannot reach the speeds other people are getting don't be too disappointed, and defiantly don't push it beyond its limit.

Now let's get to the fun part!

1) Open Core Temp (use SpeedFan if Core Temp is not compatable with your hardware) and look at the temperatures of your CPU. Focus on the readings from the core(s) or your CPU. Minimise the program so you can see the temperature(s) in the taskbar.

2) Open OCCT and run a stress test with the default settings (30min stress test for both RAM and CPU).

3) Click the green ‘ON' button and allow the stress test to run.

4) Every five minutes or so, look at the CPU temperature in the taskbar. If the temperature reaches 60oC, you should invest in some aftermarket cooling if you intent to continue and overclock. If the temperature(s) exceed 65oC, stop the stress test by pressing the ‘OFF' button.

5) If your CPU runs under 60oC under stress, overclocking is safe to perform. When OCCT is finished, minimise it.

6) Open ClockGen (try SetFSB if ClockGen doesn't support your hardware) and click on the ‘PLL Setup' button. If the drop-down box under ‘Clock Generator Setup' says "Not specified", then go here to set it up. If your chipset is not supported, then you cannot overclock via Windows using this tool (find another tool if possible or overclock via the BIOS instead). If the drop-down box shows your chipset's name, then continue to the next step.

7) Exit the ‘PLL Setup' window and click the ‘PLL Control' button. This is where you can adjust the Bus Speed/HT Bus (the first slider) and the PCI-e clock (second slider).

8) Using your knowledge gained in the ‘Theory' section of this tutorial, raise the Bus Speed/HT Bus up by an appropriate amount (e.g. 10MHz, or more if you know the CPU can handle it). Notice how the Bus Speed/HT Bus is called the 'FSB' in this program. The settings do not take effect until you click the ‘Apply' button.

9) Click ‘Apply' when you've raised the speed. Now restore OCCT and run the default stress test again.

10) If the temps are still within the 60oC limit and the computer is still stable (not frozen), repeat steps 8 and 9 again until stability is lost.

NOTE: With AMD systems, keep an eye out for the LDT Bus Speed (use CPU-Z) and adjust the HT multiplier via the BIOS where appropriate. Also remember that some CPUs (both AMD and Intel) are multiplier unlocked so you can adjust the multiplier via the BIOS or CrystalCPUID if required.

11) Once the PC is no longer stable, underclock the CPU to the last known stable frequency. Now run OCCT but set it to test the RAM only. If that is successful, do the same but test the CPU only. If both are successful, overclock the system a little further and test both components separately again. Repeat this until one of the tests fail. If the RAM is the problem, go to step 12. If the CPU is the problem, go to step 13. If both CPU and RAM seem unstable, follow steps 12 and 13, then repeat steps 8, 9, 10 and 11 until either the temperature is too high, or voltage increases don't help. If this is the case, go to step 14.

12) If your research indicates that a VDIMM increase improves stability for your model RAM, then go into the BIOS and increase it a little. (See your motherboard manual or the 'Overclocking a CPU and RAM via the BIOS' section of this tutorial to find out how to do this.) If a voltage increase doesn't help, try using a divider. Then repeat steps 8, 9, 10 and 11 again. If you get the same result as before, you have reached the limit of your system. In that case, continue to step 14.

13) Increase the voltage slightly using CrystalCPUID or the BIOS. Now repeat steps 8, 9, 10 and 11 again. If you get the same result as before, try a larger voltage increase. Remember that increasing the VCore creates more heat and can shorten component lifespan. If the heat gets too high, or the voltage reaps no benefits, you have reached the limit of your CPU. In that case continue to step 14.

14) By now you have reached the limit of your CPU and RAM. Now that you cannot overclock further without you PC being unstable, close OCCT and open Orthos Prime instead.

NOTE: If your CPU has more than 2 cores, use two instances of Orthos Prime as it only stresses 2 cores at a time.

15) Click the ‘Start' button and allow Orthos Prime to run for 4 hours (run it for 8 hours if you require highly accurate processing).

16) If the stress test fails, slightly underclock the CPU and RAM and repeat steps 15 and 16 again until the PC is stable.
Congratulations! You now have an overclocked PC. Feel free to experiment with different methods of testing. You can use CPU-Z to view the settings/speeds you are now using.

Overclocking CPU and RAM via BIOS

Part 1

Specialised Tools:

BIOS

The BIOS (Basic Input Output System) is where you can control and tweak your hardware. Tweaks generally include voltage modifications such as VCore and VDIMM, and other controls such as dividers, multipliers and bus speeds. Performance motherboards have more options which allow advanced overclocking (latency modifications etc.) and also permit higher bus overclocks due to higher quality components and firmware. The generic way to access the BIOS is to repeatedly press the [Delete] button while the computer POSTs (Power On Self Test). POST occurs as soon as you turn the PC on. Most motherboards will show a message such as "Press Del to enter setup..." where 'setup' is another name for the BIOS. If the delete key doesn't work, check your motherboard manual for more information on accessing the BIOS.

Overclocking the CPU and RAM

As mentioned previously, research the parts you intent to overclock so you have an idea of its limits. Searching the component name in Google (e.g. "E4400 overclock") should yield useful results.

Now let's get into it!

1) Follow steps 1 - 5 from the 'Overclocking the CPU and RAM via Windows' section of this tutorial.

2) Restart the PC and enter the BIOS. The BIOS used in this example is from an AMD based motherboard ('GA-K8N Pro-SLI' to be exact).

3) Firstly we're going to check out the temperature/fan settings used in the BIOS. Use the arrow keys to navigate to the 'PC Health Status' menu (or your BIOSs equivalent menu, if available) and hit [enter].

4) In this section we can alter temperature warnings and fan settings while getting readings from any thermometers embedded in the hardware. It is not necessary to alter these settings, but it can help if fan speeds need to be adjusted or to modify any temperature alarms. Go back to the BIOS menu list by pressing [Esc].

5) Most BIOSs will hide the advanced options. Use a search engine to find the key combination that your motherboard requires to unlock these options (if applicable). 'Ctrl+F1' is often used by Gigabyte motherboards.

6) An extra menu should now be available to you. In this case it's the 'MB Intelligent Tweaker (M.I.T.)' menu.

7) The M.I.T. section will provide you with all the tools you need to overclock your system. Enter this menu and have a look around. Try to work out what some of the options mean based on the theory section of this tutorial. If you're confused, don't worry, the basic functions will be discussed further on. Don't change anything just yet.

8) The first option in this particular BIOS is the 'HT Frequency ratio'. This is essentially the HT Multiplier. It is sometimes confusing when people/programs use different names to describe the one thing, but your experience will eventually prevail, so don't be too withdrawn. The best thing to do when confused is to look at the available options. Press [Enter] to view all available options for a particular setting. In this case, the options include '1x', '1.5x', '2x', '2.5x', '3x', '4x', '5x' and 'Auto'. It is obvious that this is some type of multiplier setting because the options are multiples. The name 'HT Frequency ratio' should hint that this multiplier is the 'HT Multiplier'. A quick Google search should help determine any uncertainties. Remember that the HT Multiplier is only existent on AMD CPUs. For those of you overclocking Intel CPUs, the HT Multiplier is not used and therefore the option will be unavailable.

Based on what you learnt in the theory section, you may adjust the HT Multiplier. 5x is usually the stock setting; most overclockers prefer 4x to allow more headroom when overclocking the Bus Speed. If it's set to 'Auto', change it to either the stock multiplier setting (you may have to use Google to research what this is) or change it to a lower setting as mentioned above.

Overclocking CPU and RAM via BIOS

Part 2

Other Settings

Before we continue to the next step, let's have a look at a couple of useful settings. Use these during overclocking if required.

Adjusting the CPU Multiplier

If your CPU features an unlocked multiplier, you can change it via the BIOS. To do this, enter the M.I.T. menu (or your motherboards equivalent menu) and select the 'CPU Clock Ratio' setting (or your motherboards equivalent setting). Hit [Enter] to see the available options. Use your knowledge from the 'theory' section to determine which option to use, otherwise leave it on the default multiplier.

Adjusting the HT Link Voltage

AMD systems use a HT Link (also known as a LDT Bus). When the HT Link exceeds 1000MHz - 1100MHz, most PCs become unstable. The easiest fix is to lower the HT Multiplier (recommended) but some people increase the HT Link voltage instead. To do this, enter the M.I.T. menu (or your motherboards equivalent menu) and select the 'HT-Link voltage control' setting (or your motherboards equivalent setting). Hit [Enter] to view the available options. Increase the voltage by the smallest increment available and then test for stability.

Now that you know how to access and alter these settings, continue to step 9.

Overclocking CPU and RAM via BIOS

Part 3

9) Use the arrow keys to select the 'CPU Frequency' setting. As you may have guessed, this setting allows you to alter the Bus Speed/HT Bus of the CPU. Increase this setting by an appropriate amount (10MHz, or more if you know your CPU can handle it). Now save the settings and exit the BIOS. This is usually achieved by pressing [F10] on your keyboard.

10) Boot into Windows. Run OCCT and Core Temp. With OCCT, run a stress test with the default settings (30min stress test for both RAM and CPU). Press the green 'ON' button to start the process.

11) Keep an eye on the temperature of each CPU core. If either surpasses 60oC, don't overclock further. Any temperatures over 65oC warrant the cancellation of the stress test and perhaps an underclock.

12) If the stress test is successful, restart the PC and go back into the BIOS. Repeat steps 9, 10 and 11 until the PC becomes unstable.

13) Once the PC is no longer stable, underclock the CPU to the last known stable frequency. Now run OCCT but set it to test the RAM only. If that is successful, do the same but test the CPU only. If both are successful, overclock the system a little further and test both components separately again. Repeat this until one of the tests fail. If the RAM is the problem, go to step 14. If the CPU is the problem, go to step 15. If both CPU and RAM seem unstable, follow steps 14 and 15, then repeat steps 9, 10, 11, 12 and 13 until either the temperature is too high, or voltage increases don't help. If this is the case, go to step 16.

14) If your research indicates that a VDIMM increase improves stability for your model of RAM, then you may go into the BIOS and increase it a little. To do this, enter the BIOS and go into the M.I.T. menu (or your motherboards equivalent menu). Select the setting 'DDR voltage control' (or your motherboards equivalent option) and hit [Enter]. A list of options will be available to you; choose the next step up from stock and then repeat steps 9, 10, 11, 12 and 13.

If a voltage increase doesn't help, try using a divider. To do this, get into the BIOS and enter the M.I.T. menu (or your motherboards equivalent section). Select the 'CPU / DDR clock Ratio' setting and hit [Enter]. Depending on the BIOS, the dividers will be ratios or fractions (like shown below). AMD based motherboards generally use fractions (as explained in the 'theory' section of this tutorial). Use your knowledge from the 'theory' section to determine the best divider for your setup. Repeat steps 9, 10, 11 and 12. If you get the same result as before, you have reached the limit of your system. In that case, continue to step 16.

15) Increasing the VCore often solves stability issues. To alter the VCore, go to the M.I.T. menu (or your motherboards equivalent section) and select the 'CPU Voltage Control' setting (or your motherboards equivalent setting). Increase the voltage by the smallest amount possible; in this case it's .025v at a time. Repeat steps 9, 10, 11 and 12. If you get the same result as before, try a larger voltage increase. Remember that increasing the VCore creates more heat and can shorten component lifespan. If the heat gets too high, or the voltage reaps no benefits, you have reached the limit of your CPU. Continue to step 16.

16) By now you have reached the limit of your CPU and RAM. Now that you cannot overclock further without you PC being unstable, boot into Windows and run Orthos Prime.

NOTE: If your CPU has more than 2 cores, use two instances of Orthos Prime as it only stresses 2 cores at a time.

17) Click the ‘Start' button and allow Orthos Prime to run for 4 hours (run it for 8 hours if you require highly accurate processing).

If the stress test fails, slightly underclock the CPU and RAM and repeat steps 17 and 18 again until the PC is stable. Congratulations! You now have an overclocked PC. Use CPU-Z to examine the new speed of your PC.

Benchmarking

I was going to end the tutorial without discussing benchmarking, but I then remembered that half the fun of overclocking is to see results. Benchmarking allows you to compare the performance of your PC at stock with the performance after an overclock. It also allows you to compare results with friends and people on the Internet. I recommend using the following:

3DMark06 Basic [Download - Freeware]
Tests the 3D capabilities of your PC by running graphical scenarios. Both GPU and CPU are tested and a score is calculated reflecting the performance of your system.

SuperPI Mod [Download - Freeware]
Can be used to check stability, speed and accuracy of a CPU when calculating the number Pi. The faster the CPU, the faster the calculation.

PCMark05 Basic [Download - Freeware]
Similar to 3DMark but instead benchmarks your whole computer system to determine performance.

These programs are fairly straightforward. I will not discuss how to use these programs in this tutorial, but I'm sure you'll find it quite easy compared to overclocking. For those of you who require assistance, post a thread in our Discussion Forum.

Cheat Sheet

Intel
CPU Clock Speed = Multiplier x FSB (also known as Bus Speed)
DDR RAM Clock Speed (on 1:1 ratio) = 2 x FSB (also known as Bus Speed)

Use dividers to get the most out of your system.
Modify voltages when required.

AMD
CPU Clock Speed = CPU Multiplier x HT Bus (also known as FSB or Bus Speed)
LDT Bus = HT Multiplier x HT Bus (also known as FSB or Bus Speed)
DDR RAM Clock Speed (on 1:1 ratio) = 2 x HT Bus (also known as FSB or Bus Speed)

Remember to keep the LDT Bus/HT Link close to stock.
Use dividers to get the most out of your system.
Modify voltages when required.

Final Word

As most of you would now know, overclocking is quite easy after some practice. After all this reading and tampering with bus speeds, you're probably feeling a sense of relief and admiration of your accomplishment. But there's more! Soon enough I will be writing a tutorial on advanced overclocking techniques. I'm not a professional overclocker, so I'll probably be learning a thing or two while writing it. However, rest assure that the tutorial will be full of examples and step-by-step instructions just like this one. And a hell of a lot more fun. :)

Did this guide help you overclock your computer system? Leave a comment below and let us know!

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