I'm going to run through the basics of overclocking, and the impact it has on games. If you're a veteran overclocker bear with me.
- What Is Overclocking?
Overclocking is the process of increasing the clock speed of a component of your PC. The "clock" referred to is a specialised oscillator pulsing with a frequency that determines the rate at which a processor can perform instructions. A 2 Gigahertz Pentium 4 for example has a frequency of oscillation of around 2 billion pulses per second. The theory of overclocking is simple: increase this clock speed and you'll increase the rate at which instructions are performed - ergo you have a faster PC.
This is similar to the way in which increasing the revs on an internal combustion engine means it can work faster. It's interesting to note that just like the engine, a PC which is now running faster will often also require more fuel (voltage) and cooling to perform correctly, otherwise just like the engine you risk overheating, a shut down, or even permanent damage. At the very least, it is well known that overclocking - depending on component tolerance and cooling - will reduce the life of your components, even if this is as trivial as getting 5 years out of a CPU instead of 10. On the other hand, if done correctly and within reason, overclocking will give a noticeable system performance boost for at most the cost of some extra cooling.
In practice system overclocking is usually done by increasing the Front Side Bus (FSB) speed in the BIOS. The FSB is the main pathway between your major system components, and as the FSB speed increases, information is transferred back and forth more rapidly as all your major components work off this bus speed. However there are certain problems with increasing the FSB. To start with, some components running off this bus, such as your AGP graphics card and PCI devices (e.g. Sound card) operate at a much lower bus speed by default, so your motherboard has special Dividers/Multipliers to maintain the PCI and AGP bus speeds at or close to their default (typically ~ 33Mhz for PCI and 66Mhz for AGP).
As you increase the FSB, your CPU speed will increase. Your RAM speed may also increase (depending on the memory divider/multiplier), which increases the amount of information the RAM can transfer back and forth with the CPU (referred to as Bandwidth). This improves performance but increases the stress on your RAM. At the same time, depending on your PCI/AGP dividers, the bus speeds on your graphics card and PCI devices may also increase. These devices can malfunction at higher bus speeds. All the while, as your system speed increases, at some point certain components, particularly the CPU but to some extent the RAM and AGP port, will require more voltage to fuel this increased performance. You can increase the voltage through your BIOS, but greater voltage equals greater heat, for which the standard cooling on your components - typically a metal heatsink with a fan on top - will no longer be adequate. Now you begin to appreciate the delicate balancing act which is overclocking!
For more information on FSB overclocking, check out our FSB Overclocking Guide, and for more on how heatsink cooling works, try our Heatsink Theory Guide. That's just the start. If you're interested, start searching for more information on overclocking.
- How Do I Overclock?
The main components which can be overclocked successfully for higher overall system performance are your CPU, RAM and Video Card. Now before you think I'm going to begin covering the actual steps required to overclock your PC, believe me it's too long and detailed and varies too much from system to system to be covered here. Some good starting points for finding out more are Beginner's Guide to Overclocking at Overclockers.com, a good site to pursue this topic, and this basic Overclocking Help Guide. We also have a Beginner's Guide to Overclocking nVidia Video Cards here at TweakTown which will show how a video card can be overclocked. Note that along with the utilities mentioned in that guide, I highly recommend RivaTuner for overclocking and tweaking your nVidia based video card, or PowerStrip for ATi (and nVidia) cards.
The main aim of covering overclocking here is to give you some guidance on the impact of overclocking when optimizing your system, particularly for gaming.
- Overclocking and Games
Overclocking is a strange thing indeed. It's as much luck as it is science. Two people with identical systems will achieve different levels of overclock successfully (i.e. with stability and performance) due to factors such as different build qualities/dates of the components, different environmental conditions such as ambient temperature and humidity, different BIOS versions/settings, and finally different operating system and driver settings.
It's important to remember therefore that even if you've heard of "the same" machine as yours running at much higher speeds, your system could be limited by a number of factors and therefore you just might be pushing it too far in trying to reach this "guaranteed" speed.
Any time you overclock your system you are pushing it beyond specifications, so don't be surprised if this manifests itself in some very strange and unpredictable ways. Everyone who overclocks is familiar with some of the more noticeable problems of an unstable overclock: system freezes/resets/crashes to desktop, Windows blue screen errors (also called the Blue Screen Of Death - BSOD), registry corruption errors, PC not loading up or stopping part-way through loading, PC not even getting past POST (with beeping errors), and so forth.
While some of the above are clearly due to overclocking, some people don't realise that less frequent freezing/resets, strange application behaviour (not starting correctly, crashing to desktop at some point, flickering, graphical glitches, strange AI behaviour), corrupt downloaded files, corrupted files copied to/from the hard drive and/or CD/DVD-ROM, badly burnt CDRWs etc. are the more subtle signs of overclocking-related errors. This is something you should not put up with. There's no reason why your system can't be stable 99% of the time, especially if you run a recent operating system like Windows XP.