Beginners Guide To Overclocking: Part 1

By: Jurtje (and OCIA.net forum members)

Introduction

This is my attempt to help the beginner enthusiast overclock their computer. Please be aware that I am in no way an expert; I’m not an electronics engineer. I’m just a hobbyist and have gathered my knowledge from the help of other members of the OCIA.net forums as well as reading articles on the net.

So what exactly is overclocking and why would anybody want to do it? Overclocking is the art of pushing your system to the limits; squeezing every last bit of power and performance out of your components. Overclocking is an enthusiast hobby. A good comparative example would be a car enthusiast. Sure, you can spend hundreds of thousands of dollars to own some of the fastest cars in the world, but why bother when you can take virtually any car, and make it just as fast with the right modifications for a fraction of the price?

An overclocker has the same mindset. You can make your system perform identical to or even better than a more expensive system... for free!

Before we go any further, let's consider the following:

Overclocking can be dangerous to your computer components. You can easily overheat, for example, your processor, and render it useless. A good rule I’ve read somewhere says: “If you can’t afford to replace the parts, don’t overclock!” Overclocking voids the warranty on your CPU and possibly other components. Also, neither I nor OCIA.net will be responsible if something goes wrong with your overclock.



A dead AMD Athlon 1800+ XP, courtesy of www.slapps.com

However, if you’re careful and watch your temperatures closely, it’s pretty hard to actually fry something. In this guide, I have assumed that you, the reader, have some prior knowledge of your computer’s hardware, the BIOS and operating systems in general.

By far, not all systems can be overclocked. Laptops are pretty much out of the question. Macs can sometimes be overclocked by changing jumpers, although our focus in this guide is strictly the PC. Most importantly, any OEM (original equipment manufacturer) computer, such as a Dell, HP or E-machine, will be virtually impossible to overclock. These manufacturers have hidden all “overclocking” settings in the BIOS. The only chance you have to overclock an OEM system is by either finding a hacked BIOS on the internet (allows you to change these settings, although often difficult to find) or trying to overclock by means of a software program (unstable, few options).

If you plan to overclock, your best bet is to purchase or build a custom system. This gives you the ability to pick and choose what components you want in your system.

Not all aftermarket motherboards can be used to overclock. Be sure to do your homework before deciding on which board to purchase.

Overclocking is best done in the computer’s BIOS (Basic Input Output System). There are some software programs available which allow you to overclock inside the operating system, but the best results are achieved by changing BIOS settings. Usually you can get into your BIOS by pressing DEL as soon as your computer begins to post (when it shows the RAM size, processor speed, etc.). Check your motherboard manual for further details. You will want to look for a section entitled “ CPU Speed” or “Advanced Chipset Features”.



Here you can change your FSB (front side bus), memory timings (discussed in part 2 of this guide) and also your CPU multiplier (also referred to as CPU Clock Ratio). Remember, not all motherboards have overclocking options.

Clearing your CMOS

Whenever an overclock becomes unstable or your computer will not boot, you will need to reset the BIOS back to default and start over again. This is done by clearing the CMOS (a small piece of memory on the motherboard which remembers your BIOS settings and is powered by a little battery).

Some newer motherboards (such as the ASUS A7N8X series), will clear its CMOS after a faulty overclock by just turning the computer off then back on. However, most motherboards require a manual clear. This can be done in two ways, depending on your motherboard.

The first way is by changing the position of the clear CMOS jumper on your motherboard, waiting a few minutes, then repositioning the jumper to its original place.



The second way, if your motherboard doesn’t have this jumper, consists of unplugging your computer, removing the little CMOS battery, powering up your computer (your capacitors will discharge), and waiting a couple of minutes. Then you have to reseat the battery and plug in your computer.

Now that your CMOS is cleared, all BIOS settings are reset back to default and you’ll have to start the overclocking process all over again.

Continue ahead as we look at the difference between locked and unlocked processors...

Locked or unlocked

The first thing to know when we start the process of overclocking, is whether our processor is multiplier locked or unlocked.

To check whether your CPU is locked, lower your multiplier via the BIOS one step, for example from 11 to 10.5. Save and exit your BIOS and your computer will restart. If your computer posts again and shows the new CPU speed, it means your CPU is unlocked.

However, if your computer failed to post (screen remains black) or no CPU speed change is present, this means your multiplier is locked.

Multiplier unlocked processors

Step one:

Usually (considering you have good cooling) your max overclock is limited by your memory, or RAM. A good starting place is to find the top memory bus speed in which your memory can handle while keeping it in sync with the FSB.

To check this, we’ll lower our CPU multiplier some steps (from 11 to 9, for example) and we’ll increase our FSB a few notches (e.g.: 200 MHz to 205 MHz). Save and exit your BIOS.

There are a few ways to test for stability. If you make it into Windows, that is a good start. You can try running a few CPU / RAM intensive programs to stress these components. Some good examples are SiSoft Sandra, Prime95, 3DMark 2003 and Folding@Home. You may also choose to run a program outside of Windows, such as Memtest. Load a copy of Memtest onto a bootable floppy, then insert the disk after you have exited the BIOS. If the computer does not detect the floppy, you might want to check the boot order of your devices and ensure that floppy is first (for now, anyway).



Memtest86+ running, from the Memtest86+ website.

Continue to increase your FSB until Memtest starts reporting errors. When this happens, you can try to increase the voltage supplied to your memory. Do note that increasing voltages may shorten the life span of your memory. Also, another option is to loosen the timings on the memory (more on this a bit later). The previous FSB setting before the error will be your max FSB.

Your max FSB will fully depend on what memory you have installed. Quality, name-brand memory will work best for overclocking. For reference, below is a quick chart showing the most common memory speeds, and their actual speed:



If you have high quality memory, such as that from Corsair, Crucial, or OCZ (just to name a few), then you may be able to run, say, PC2700 @ PC3200 speeds. Or you can buy real overclocking memory which is rated at higher speeds, for example PC4000.



Step two:

Now that we know our max FSB, we’ll figure out our max multiplier. Keeping our FSB @ stock, we raise our multiplier one step at a time. Each time we restart, check for system stability. As mentioned above, one good way to do this is by running Prime95.



If it doesn’t post (reread the section about clearing the CMOS), or Prime 95 fails, you can try to raise the core voltage a bit. The core voltage is the voltage which is being supplied to the CPU (also known as Vcore in the BIOS). Increasing it may or may not increase stability. On the other hand, the temperature will also be increased. If you are going to increase the core voltage, you should keep an eye on temperatures, at least for a few minutes. Also note that increasing voltages may shorten the life span of your CPU, not to mention void your warranty.

When your computer is no longer stable at a given multiplier setting, lower your multiplier one step and take that as your max multiplier.

Step three:

Now that we have our max FSB speed and our max multiplier, you can play around and determine the best settings for your system. Do note that having a higher FSB overclock as opposed to a higher multiplier will have a greater impact on overall system performance.

Multiplier locked processors

Having a multiplier locked processor means that you can only overclock by increasing the Front Side Bus. The majority of newer model CPU’s fall into this category. We’ll just follow the same strategy as applied in step one of the unlocked processors chapter.

Basically, raise the FSB in small increments, and after each post, check the system for stability (Prime95 or Memtest). Also remember that increasing your CPU or RAM voltage can give you more stability. When you reach your peak FSB (probably because of your memory), you can try to get a little further by relaxing your memory timings (again, more on that in a bit).

Next up we have a few tips on obtaining a stable overclock...

Getting your system stable

Now that we have an initial overclock, whether with a locked or unlocked processor, we have to tweak the system to get it absolutely stable. This means we have to change the variables (Multiplier, FSB, voltages, memory timings) until the system is rock solid.

This is mainly a trial and error process and takes up most of the time when overclocking a system. I can’t really give you a step by step procedure, since it depends on so many variables. But I can give you some thoughts:

- Your system will start acting strange if your motherboard doesn’t have a PCI /AGP lock. Having a PCI/AGP lock will keep the frequency of your PCI and AGP bus at 33 and 66 MHz respectfully, even if you raise your FSB. Without this lock, the PCI and AGP bus speeds are increased with the FSB, eventually reaching a point where they no longer function correctly. Some motherboards have this lock and some don’t. Sometimes it even depends on the BIOS revision as to whether or not it is present. BIOS revisions can be found at the motherboard manufacturers website. Check your motherboard / BIOS for such an option.

- Remember that increasing your voltage will almost always make your system more stable. But as stated several times before, your temperature will sky rocket and the components lifetime may be decreased. Therefore, the goal is to find the lowest voltage settings at which your system is stable.

- Decreasing your FSB a few notches may also provide a stable overclock. Sure, you may not want to lower your max overclock, but lowering your FSB 1-2 MHz can mean the difference between a stable system and a BSOD (Blue Screen of Death) after 25 minutes of Far Cry .

- Sometimes, a very high temperature can cause instability as well, so be sure to keep your processor at a decent temperature.

- One of the ultimate stress tests is Prime 95. When you think your system is stable, run the blend torture test for 12 hours and see if you get any errors. If you don’t, then you should be set. If errors are present, go back to the drawing board. Lower your FSB, increase your voltage, relax your memory timings, etc.

Be on the lookout for part 2 of our overclocking guide, which should be released very soon.