Ahh... the grandmother of all overclocking articles has come into being. Aren't you excited? And as Trent Reznor (NIN) might say, "Doesn't it make you feel better?" Truth is, we at Tweak3D have only briefly gone over what goes into overclocking a computer while making sure it is as stable as granite, and I intend to change that - now!
Overview
Here's a basic outline of the kind of stuff you will find in this guide.
- Necessary tools
- Safety precautions
- Bus Clock Speed
- Bus Clock Multipliers and Multiplier Locks
- Chip Voltage and Stability
- Cooling!
- The Overclocking Process
- Stability Testing Procedures
- Troubleshooting a Failed Overclock
- Electrostatic Migration and Burnout
- Overclocked Processor Lifetime
- Effect of Non-standard Bus Speeds on Other Computer Components
- Alternative Methods of Overclocking
Necessary Tools
There are several things you need to know before you begin trying to overclock a computer. Depending on the part of the computer you are trying to overclock and how far you are going to take the process, you may need any or all of the following things:
- Phillips head screwdriver
- Flat head screwdriver
- Tweezers
- Thermal Paste
- Thermal Tape (FragTape)
- A flat razor
- Cooling fan/Peltier/etc.
- Application Specific Tools (ex: Peltier cooling systems may require insulation)
Make sure you have ALL the tools you need before you begin working (in some cases, you may not need any tools at all). Make sure you are in a clean, well-ventilated area, with plenty of workroom (if you will be taking on a larger project).
Safety Precautions
There are a couple of very important things to keep in mind when you are attempting to overclock a computer, so that you don't damage your equipment. The first of these things is to make sure you have adequate cooling to take on the project you are planning. As will be discussed later, cooling can make or break an overclock - but that isn't its only benefit. It also helps prevent damage being done to the chips due to excessive heat.
Ok, now that I have taken care of explaining the importance of cooling to you, on to the (second) most important safety precaution - which has to do with progressive overclocking. I know, I know, that isn't a term most people have ever heard of - and that's because I just coined the term. Progressive overclocking has to do with the process of slowly clocking your system faster and faster until it reaches its peak stable speed. This is frequently done with video card overclocks, because it is very easy to over do it and fry the card. The process with video cards is very easy - you simply overclock in 5 MHz increments until you reach an unstable speed, and then downclock the card in 1 MHz increments until you reach a stable speed. Then of course comes the obligatory testing to determine whether or not the card is stable even during system strain - and if it passes, you're gold.
However, the process with a CPU is more difficult - mainly because it is hastlesome to go back into the BIOS for every clock change. With bus clocks, bus multipliers, and chip voltages to contend with, things aren't always hunky-dory.
Bus Clock Speeds
The system bus clock is a very important concept when dealing with system overclocking, particularly when you are dealing with an Intel-based system. This is because Intel's processors are multiplier locked. More on that subject later, however. Right now I want to explain to you about the system bus and how it can effect your system.
The bus clock I am referring to is the system bus on which the processor communicates with the rest of the computer. It is derived directly from the computer's internal quartz crystal which runs at ~12 MHz (and subsequently also runs the computer's internal clock). This bus speed, when taken into account with the processor's bus multiplier, determines what speed the CPU runs at, as well as some other things. You see, the PCI and AGP slots derive their bus speeds from the system clock (33 and 66 MHz respectively) using a bus divider. These dividers have been set up specifically for the standard system bus speeds (66/100/133), but don't work quite as well for the non-standard bus speeds. That means that, unless you are jumping from 66 to 100 MHz, or from 100 to 133 MHz, you will also have to over or under clock your system buses - and sometimes they don't take kindly to the extra stress.
System Bus Multiplier and Multiplier Locks
The system bus multiplier takes the system bus * whatever the multiplier is to determine the speed at which the processor is running. That means that a computer running at the 100 MHz bus speed with a 4.5 bus multiplier would be running at 450 MHz. Simple enough to overclock your computer without messing with the system bus, right? Wrong. Why is that? It is because Intel had the audacity to lock the clock multiplier on its processors. That means that your computer HAS to use the 4.5 bus multiplier to derive the processor's clock speed, and dramatically limits the speed range of most processors. This, combined with the fact that most computer components don't function properly on non-standard bus speeds, makes overclocking most computers difficult (to get a completely stable system you have to jump up to the next standard bus speed - a mighty task for most processors).
Of course, AMD has (sort of) come to the rescue by not locking the system multiplier. However, to change the setting, you have to break the chip's casing open, hence voiding the warranty (overclocking voids your warranty anyway - so no big deal). They were even so nice as to include an edge connector to allow the connection of third-party jumpers to make overclocking a snap. Of course, you get the best results using a soldering iron... but that's an entirely different article.
Chip Voltage and Stability
Chip voltage can turn a not-quite-so-stable chip into rock hard granite. Most CPU's have some sort of way to change the voltage of the chip. Raising (and in some rare cases, lowering) the chip's voltage can create a much stabler chip, at the cost of more heat. Heat, of course, alternately lowers the overclockability of a chip, but it doesn't lower the chip's overclockability as much as upping the voltage raises it. And besides, there is always cooling. But more on that later.
The basic theory on chip voltage and how it affects the processor is this: a higher chip voltage increases the signal strength between transistors within the chip, allowing the signal to ignore greater discrepancies within the silicon core itself. You see, the silicon wafers used to make the chips aren't always pure, and they definitely aren't all of the same quality. A chip with a higher clock rate is generally going to have a core made of a higher quality silicon wafer (something that can't be determined until after fabrication, due to the fact that all the wafers are as pure as they can make them).
Now, the processor signal has two choices as to how to deal with a chip impurity (how it is dealt with has to do with quantum physics and really isn't imperative to this discussion). It can either jump the gap, or go around it. When the processor frequency is lower, the signal has the time to go around the defect if need be, but if the frequency is too high and the signal must go around, the signal doesn't get to its destination in time or at all (remember we are dealing with millionths or billionths of seconds), causing a miscalculation that usually will cause some form of software error (commonly it causes a crash).
However, upping the core voltage is like giving the signal a running start, it allows the signal to jump gaps within the chip with relative ease (sort of like a lightning arc), and the signal gets to it's destination in time.
Cooling
Two of the parts of the overclocking process up the heat produced by the processor - upping the frequency (the actual overclock) and upping the core voltage. Excessive heat within the core creates more of those gaps that I was discussing above for the signal to cross, and too many of these gaps will weaken the signal to the point where it becomes non-existent and creates some more of those wonderful software errors. Here's the lowdown for you physically inclined folks - the extra heat energizes the particles within the silicon wafer. The pathways within the silicon wafer are approaching the size of light rays (read very small), so if the particles move too much, they break their connection with the other particles within the pathway. These temporary breaks do the same thing as the impurities mentioned above. Got it? Good.
Ok, now that you know all about why cooling is so important, here's the skinny on what kind of stuff is available to you hobbyist overclockers out there, and then maybe I'll do a little of the honorable mention thing to the more expensive cooling systems of the world. The simplest way to cool your chip is called passive air-cooling. Passive air-cooling is basically the use of the surrounding, cooler air to cool the chip, using some sort of ball bearing fan. This is the cheapest, easiest, and most common way to cool your processor - all it entails is attaching a fan/heatsink combo to the processor to cool the thing down.
Hard-core hobbyists, however, are never satisfied with simple 'air' cooling, oh no. Heck, I've even seen some guys go so far as immerse their systems into super-cooled glycerin (a non-conductive liquid) to cool their processors. But that, once again, is a subject for another article. There are two 'reasonable' types of active chip cooling. One, a Peltier system, basically uses a heat-transfer plate (called a Peltier) to conduct heat away from the processor, where it is then carried off by a standard fan/heatsink combo. The only extra stuff you need for this type of system is some form of insulation for the exposed portion of the cold side of the Peltier, because otherwise you will get condensation, and even frost (Peltiers are extremely efficient).
The other 'standard' form of active cooling is using some form of water cooling device. These devices are extremely complex, and on top of the mandatory insulation, you also need a pump and some form of condenser... for the average hobbyist, it would be easier to put your computer in the freezer and run the wires out through a self-drilled hole rather than set one of these bad boys up.
Of course, you always have the "professionally" overclocked systems from companies such as Kryotech. Kryotech uses a method of cooling called "liquid phase change cooling." It is extremely efficient but also extremely expensive - the special case alone costs $1000 US all by itself, not including the processor enclosure. Boy, what some people will do for a couple of extra megahertz. Anyhow, if you've got the cash, their systems are something you might want to look into.
To install a cooling device, first you need to remove the old fan/heatsink combo from your processor. This should be a fairly simple operation. Don't be afraid to use a little force to break the seal that was created by the thermal compound. You will then need to use a flat razor to remove the remainder of the thermal compound from the top of the processor. Once this is complete, apply either some more thermal compound or thermal tape (FragTape) to the top of the processor and attach the new heatsink on top of that. Simple enough, huh? Some setups may have other necessary steps to attach the cooling device (thermally insulating silicon caulking compound, etc.) to prevent condensation - but that won't be a problem with a standard fan/heatsink combo.
Conclusion
Well, there you have it - the first part of the overclocking how to guide. In the next part, I will be covering the actual overclocking process, and some other nice little tidbits. It should be posted tomorrow or the day after. And of course, feel free to email me with any comments or questions.
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