Ultimate Overclocking & Stability Testing

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INDEX


Part 1.: Ultimate Overclocking Guide - Click here

Part 2.: Ultimate Stability Testing - Click here

Part 3.: Test Your PSU's Rails With A Multimeter - Click here

~Disclaimer!

Everyday the number of persons, who are interested in overclocking rises. Also rises the number of overclocking computers number, and the number of ‘burned out’ systems. A lot of people are trying to overclock their precious system on their own, without knowing what the hell they’re doing. Hopefully todays systems are made with a lot of safety functions and this doesn’t really allow the person to ‘burn out’ their system, just like locking up, or rebooting due to high temperature, and then resetting itself the bios, and notifying the owner that the system has just recovered from an unstable overclock, and the bios settings are set to the default one. Also there are a lot of people who are ‘lazy’ and they don’t use Google or read the stickys at forums.

So, I decided that I’ll make a thread, where I’ll gather all the information (at least I’ll try – because it’s nearly impossible to gather all) what’s possible about overclocking, and to put them in one place in a clear and easy way, so that everybody can understand it.

In this guide, I just want to explain as clear as possible, what’s overclocking, how to overclock, how to troubleshoot an overclocked system, and everything what’s related to overclock. This will NOT be my own guide, I will be using lots of other sources (I will mention at the end of guide, those other sources, giving direct-link to them), but the idea is to have all the information at a single & same place, and people can read this, and understand how to overclock their system without problems.

So generally speaking, this thread contains all the information (I just hope) what’s required to help you understand how to overclock. I just gathered all the information from around 6-8 guides - see the end of the guide, to see all the sources.

WARNING: Overclocking can f*ck up your stuff. Overclocking wares down the hardware and the life-expectancy of the entire computer will be lowered if you overclock. If you attempt to overclock, this forum, its inhabitants, and ‘people who are appearing at the end of guide as sources’ are not responsible for anything broken or damaged when using this guide.
This thread is merely for those who accept the possible outcomes of this overclocking guide/FAQ, and overclocking in general.

Why would you want to overclock?

Well, the most obvious reason is that you can get more out of a processor than what you payed for. You can buy a relatively cheap processor and overclock it to run at the speed of a much more expensive processor. If you're willing to put in the time and effort, overclocking can save you a bunch of money in the future or, if you need to be at the bleeding edge like me, can give you a faster processor than you could possibly buy from a store.

What is Overclocking?

Overclocking is the process of making various components of your computer run at faster speeds than they do when you first buy them. For instance, if you buy a Pentium 4 3.2GHz processor, and you want it to run faster, you could overclock the processor to make it run at 3.6GHz.

The Dangers of Overclocking

First of all, let me say that if you are careful and know what you are doing, it will be very hard for you to do any permanent damage to your computer by overclocking. Your computer will either crash or just refuse to boot if you are pushing the system too far. It's very hard to fry your system by just pushing it to it's limits.

There are dangers, however. The first and most common danger is heat. When you make a component of your computer do more work than it used to, it's going to generate more heat. If you don't have sufficient cooling, your system can and will overheat. By itself, overheating cannot kill your computer, though. The only way that you will kill your computer by overheating is if you repeatedly try to run the system at temperatures higher than recommended. As I said, you should try to stay under 60 C.

Don't get overly worried about overheating issues, though. You will see signs before your system gets fried. Random crashes are the most common sign. Overheating is also easily prevented with the use of thermal sensors which can tell you how hot your system is running. If you see a temperature that you think is too high, either run the system at a lower speed or get some better cooling. I will go over cooling later in this guide.

The other "danger" of overclocking is that it can reduce the lifespan of your components. When you run more voltage through a component, it's lifespan decreases. A small boost won't have much of an affect, but if you plan on using a large overclock, you will want to be aware of the decrease in lifespan. This is not usually an issue, however, since anybody that is overclocking likely will not be using the same components for more than 4-5 years, and it is unlikely that any of your components will fail before 4-5 years regardless of how much voltage you run through it. Most processors are designed to last for up to 10 years, so losing a few of those years is usually worth the increase in performance in the mind of an overclocker.

Basic Terms of Overclocking

Chipset - A chipset is defined as “a group of microchips designed to work as a unit in performing one or more related functions.” As a general rule, today’s chipsets consist of two parts, a Northbridge and a Southbridge. Both of these terms will be discussed later, but the two working in tandem creates a better and more efficient flow of data with fewer conflicts. Common chipsets used with the Athlon XP processor at the time include the VIA KT400 as well as the nVidia nForce2. The nForce2 has emerged as a great chipset is the choice of overclockers.

Clock Multiplier - The Clock Multiplier is an internal setting of the processor that is used to determine the processor speed. As an example, if you have a processor that is set at the factory with a clock multiplier of 10 have a FSB of 100MHz, then the resulting processor speed is 1000MHz or 1GHz. It's a very simple and easy term but used frequently.

Double Data Rate (DDR) - Double Data Rate, or DDR as it is commonly called, is becoming very popular with the computer industry lately. DDR allows for the support of data transfers on both edges of each clock cycle (the rising and falling edges), effectively doubling the memory chip's data throughput. And even better is that all of the motherboards and the Athlon processors themselves support this feature. So not only can we double the effectiveness of our memory, but we can also double the speed at which data flows between areas of the motherboard too.

Front Side Bus (FSB) - In simple terms, the Front Side Bus (FSB) is the data path between the processor and the main memory. When used from an overclocker’s standpoint it is generally referred to as a speed measured in Megahertz (MHz). The higher the number, the faster the data flows.

Northbridge - The Northbridge is the portion of the chipset that communicates with the computer processor and controls interaction with memory, the Peripheral Component Interconnect (PCI) bus, Level 2 cache, and all Accelerated Graphics Port (AGP) activities. The Northbridge communicates with the processor using the Front Side Bus (FSB).

VAGP - VAGP refers to the voltage setting of the AGP port on the motherboard. Not all motherboards allow for the adjustment of this setting, but for those that do allow for it, the benefits can be great.

VCore - This is the voltage setting for the processor. This is where you can force your speeds to the next level, or completely fry your precious CPU.

VDIMM - This is where you set the voltage levels of your memory. Though higher voltages can help you achieve better overall speeds, they can also cause some system instabilities.

The Basics

To understand how to overclock your system, you must first understand how your system works. The most common component to overclock is your processor.

When you buy a processor, or CPU, you will see it's operating speed. For instance, a Pentium 4 3.2GHz CPU runs at 3.2GHz, or 3200 MHz. This is a measurement of how many clock cycles the processor goes through in one second. A clock cycle is a period of time in which a processor can carry out a given amount of instructions. So, logically, the more clock cycles a processor can execute in one second, the faster it can process information and the faster your system will run. One MHz is one million clock cycles per second, so a 3.2GHz processor can go through 3,200,000,000, or 3 billion two hundred million clock cycles in every second. Pretty amazing, right?

The goal of overclocking is to raise the GHz rating of your processor so that it can go through more clock cycles every second. The formula for the speed of your processor if this:

FSB (in MHz) x Multiplier=Speed in MHz.

Now to explain what the FSB and Multiplier are:

The FSB (or, for AMD processors, the HTT*), or Front Side Bus, is the channel through which your entire system communicates with your CPU. So, obviously, the faster your FSB can run, the faster your entire system can run.

CPU manufacturers have found ways to increase the effective speed of the FSB of a CPU. They simply send more instructions in every clock cycle. So instead of sending one instruction every one clock cycle, CPU manufacturers have found ways to send two instructions per clock cycle (AMD CPUs) or even four instructions per clock cycle (Intel CPUs). So, when you look at a CPU and see it's FSB speed, you must realize that it is not really running at that speed. Intel CPUs are "quad pumped", meaning they send 4 instructions per clock cycle. This means that if you see an FSB of 800MHz, the underlying FSB speed is really only 200MHz, but it is sending 4 instructions per clock cycle so it achieves an effective speed of 800MHz. The same logic can be applied to AMD CPUs, but they are only "double pumped", meaning they only send 2 instructions per clock cycle. So an FSB of 400MHz on an AMD CPU is comprised of an underlying 200MHz FSB sending 2 instructions per clock cycle.

This is important because when you are overclocking, you will be dealing with the real FSB speed of the CPU, not the effective CPU speed.

The multiplier portion of the speed equation is nothing more than a number that, when multiplied by the FSB speed, will give you the total speed of the processor. For instance, if you have a CPU that has a 200MHz FSB (real FSB speed, before it is double or quad pumped) and has a multiplier of 10, then the equation becomes:

(FSB) 200MHz x (Multiplier) 10= 2000MHz CPU speed, or 2.0GHz.

On some CPUs, such as the Intel processors since 1998, the multiplier is locked and cannot be changed. On others, such as the AMD Athlon 64 processors, the multiplier is "top locked", which means that you can change the multiplier to a lower number but cannot raise it higher than it was originally. On other CPUs, the multiplier is completely unlocked, meaning you can change it to any number that you wish. This type of CPU is an overclockers dream, since you can overclock the CPU simply by raising the multiplier, but is very uncommon nowadays.

It is much easier to raise or lower the multiplier on a CPU than the FSB. This is because, unlike the FSB, the multiplier only effects the CPU speed. When you change the FSB, you are really changing the speed at which every single component of your computer communicates with your CPU. This, in effect, is overclocking all of the other components of your system. This can bring about all sorts of problems when other components that you don't intend to overclock are pushed too far and fail to work. Once you understand how overclocking works, though, you will know how to prevent these issues.

*On AMD Athlon 64 CPUs, the term FSB is really a misnomer. There is no FSB, per se. The FSB is integrated into the chip. This allows the FSB to communicate with the CPU much faster than Intel's standard FSB method. It also can cause some confusion, since the FSB on an Athlon 64 can sometimes be referred to as the HTT. If you see somebody talking about raising the HTT on an Athlon 64 CPU and is talking about speeds that you recognize as common FSB speeds, then just think of the HTT as the FSB. For the most part, they function in the same way and can be treated the same and thinking of the HTT as the FSB can eliminate some possible confusion.

How to Overclock

So now you understand how a processor gets it's speed rating. Great, but how do you raise that speed?

Well, the most common method of overclocking is through the BIOS. The BIOS can be reached by pressing a variety of keys while your system is booting up. The most common key to get into the BIOS is the Delete key, but others may be used such as F1, F2, any other F button, Enter, and some others. Before your system starts loading Windows (or whatever OS you have), it should have a screen that will tell you what button to use at the bottom.

Once you are in the BIOS, assuming that you have a BIOS that supports overclocking, you should have access to all of the settings needed to overclock your system. The settings that you will most likely be adjusting are:

Multiplier, FSB, RAM Timings, RAM Speed, and RAM Ratio.

On a very basic level, all you are trying to do is to get the highest FSB x Multiplier formula that you can achieve. The easiest way to do this is to just raise the multiplier, but that will not work on most processors since the multiplier is locked. The next method is to simply raise the FSB. This is pretty self explanatory, and all of the RAM issues that have to be dealt with when raising the FSB will be explained below. Once you've found the speed at which the CPU won't go any faster, you have one more option.

If you really want to push your system to the limit, you can try lowering the multiplier in order to raise the FSB even higher. In order to understand this, imagine that you have a 2.0GHz processor that has a 200MHz FSB and a 10x multiplier. So 200MHz x 10=2.0GHz. Obviously, that equation works, but there are other ways to get to 2.0GHz. You could raise the multiplier to 20 and lower the FSB to 100MHz, or you could raise the FSB to 250MHz and lower the multiplier to 8. Both of those combinations would give you the same 2.0GHz that you started out with. So both of those combinations should give you the same system performance, right?

Wrong. Since the FSB is the channel through which your system communicates with your processor, you want it to be as high as possible. So if you lowered the FSB to 100MHz and raised the multiplier to 20, you would still have a clock speed of 2.0GHz, but the rest of the system would be communicating with your processor much slower than before resulting in a loss in system performance.

Ideally, you would want to lower the multiplier in order to raise the FSB as high as possible. In principle, this sounds easy, but it gets complicated when you involve the rest of the system, since the rest of the system is dependent on the FSB as well, chiefly the RAM. Which leads me to the next section on RAM.

RAM and what it has to do with Overclocking

First and foremost, I consider this site to be the Holy Grail of RAM information. Learn to love it.

As I said before, the FSB is the pathway through which your system communicates with your CPU. So raising the FSB, in effect, overclocks the rest of your system as well.

The component that is most affected by raising the FSB is your RAM. When you buy RAM, it is rated at a certain speed. I'll use the table from my post to show these speeds:
Quote:

To understand what this table means, look here. Note how the RAM's rated speed is DDR PC-4000. Then refer to this table and see how PC-4000 is equivalent to DDR 500.

To understand this, you must first understand how RAM works. RAM, or Random Access Memory, serves as temporary storage of files that the CPU needs to access quickly. For instance, when you load a level in a game, your CPU will load the level into RAM so that it can access the information quickly whenever it needs to, instead of loading the information from the relatively slow hard drive.

The important thing to know is that RAM functions at a certain speed, which is much lower than the CPU speed. Most RAM today runs at speeds between 133MHz and 300MHz. This may confuse you, since those speeds are not listed on my chart.

This is because RAM manufacturers, much like the CPU manufacturers from before, have managed to get RAM to send information twice every RAM clock cycle.* This is the reason for the "DDR" in the RAM speed rating. It stands for Double Data Rate. So DDR 400 means that the RAM operates at an effective speed of 400MHz, with the "400" in DDR 400 standing for the clock speed. Since it is sending instructions twice per clock cycle, that means it's real operating frequency is 200MHz. This works much like AMD's "double pumping" of the FSB.

So go back to the RAM that I linked before. It is listed at a speed of DDR PC-4000. PC-4000 is equivalent to DDR 500, which means that PC-4000 RAM has an effective speed of 500MHz with an underlying 250MHz clock speed.

So what does this all have to do with overclocking?

Well, as I said before, when you raise the FSB, you effectively overclock everything else in your system. This applies to RAM too. RAM that is rated at PC-3200 (DDR 400) is rated to run at speeds up to 200MHz. For a non-overclocker, this is fine, since your FSB won't be over 200MHz anyway.

Problems can occur, though, when you want to raise your FSB to speeds over 200MHz. Since the RAM is only rated to run at speeds up to 200MHz, raising your FSB higher than 200MHz can cause your system to crash. How do you solve this? There are three solutions: using a FSB:RAM ratio, overclocking your RAM, or simply buying RAM rated at a higher speed.

Since you probably only understood the last of those three options, I'll explain them:

To learn more about RAM timings, go here.

FSB:RAM Ratio

If you want to raise your FSB to a higher speed than your RAM supports, you have the option of running your RAM at a lower speed than your FSB. This is done using an FSB:RAM ratio. Basically, the FSB:RAM ratio allows you to select numbers that set up a ratio between your FSB and RAM speeds. So, say you are using the PC-3200 (DDR 400) RAM that I mentioned before which runs at 200MHz. But you want to raise your FSB to 250MHz to overclock your CPU. Obviously, your RAM will not appreciate the raised FSB speed and will most likely cause your system to crash. To solve this, you can set up a 5:4 FSB:RAM ratio. Basically, this ratio will mean that for every 5MHz that your FSB runs at, your RAM will only run at 4MHz.

To make it easier, convert the 5:4 ratio to a 100:80 ratio. So for every 100MHz your FSB runs at, your RAM will only run at 80MHz. Basically, this means that your RAM will only run at 80% of your FSB speed. So with your 250MHz target FSB, running in a 5:4 FSB:RAM ratio, your RAM will be running at 200MHz, which is 80% of 250MHz. This is perfect, since your RAM is rated for 200MHz.

This solution, however, isn't ideal. Running the FSB and RAM with a ratio causes gaps in between the time that the FSB can communicate with the RAM. This causes slowdowns that wouldn't be there if the RAM and the FSB were running at the same speed. If you want the most speed out of your system, using an FSB:RAM ratio wouldn't be the best solution.

Overclocking your RAM

Overclocking your RAM is really very simple. The principle behind overclocking RAM is the same as overclocking your CPU: to get the RAM to run at a higher speed than it is supposed to run at. Luckily, the similarities between the two types of overclocking end there, or else RAM overclocking would be much more complicated than it is.

To overclock RAM, you just enter the BIOS and attempt to run the RAM at a higher speed than it is rated at. For instance, you could try to run PC-3200 (DDR 400) RAM at a speed of 210MHz, which would be 10MHz over the rated speed. This could work, but in some cases it will cause the system to crash. If this happens, don't panic. The problem can be solved pretty easily by raising the voltage to your RAM. The voltage to your RAM, also known as vdimm, can be adjusted in most BIOSes. Raise it using the smallest increments available and test each setting to see if it works. Once you find a setting that works, you can either keep it or try to push your RAM farther. If you give the RAM too much voltage, however, it could get fried. For info on what voltages are safe, refer back to the Holy Grail of RAM.

The only other thing that you have to worry about when overclocking RAM are the latency timings. These timings are the delays between certain RAM functions. If you want more info on this, you know where to look Basically, if you want to raise the speed of your RAM, you may have to raise the timings. It's not all that complicated, though, and shouldn't be too hard to understand.

That's really all there is to it. If only overclocking the CPU were that easy.

Buying RAM rated at a Higher Speed

This one's the simplest thing in this entire guide If you want to raise your FSB to, say, 250MHz, just buy RAM that is rated to run at 250MHz, which would be DDR 500. The only downside to this option is that faster RAM will cost you more than slower RAM. Since overclocking your RAM is relatively simple, you might want to consider buying slower RAM and overclocking it to fit your needs. It could save you over a hundred bucks, depending on what type of RAM you need.

That's basically all you need to know about RAM and overclocking. Now onto the rest of the guide.

Voltage and how it affects Overclocking

There will be a point when you are overclocking and you simply cannot increase the speed of your CPU anymore no matter what you do and how much cooling you have. This is most likely because your CPU is not getting enough voltage. This is very similar to the RAM voltage scenario that I addressed above. To solve this, you simply up the voltage to your CPU, also known as the vcore. Do this in the same fashion described in the RAM section. Once you have enough voltage for the CPU to be stable, you can either keep the CPU at that speed or attempt to overclock it even further. As with the RAM, be careful not to overload the CPU with voltage. Each processor has recommended voltages setup by the manufacturer. Look on the website to find these. Try not to go past the recommended voltages.

Keep in mind that upping the voltage to your CPU will cause much greater heat output. This is why it is essential to have good cooling when overclocking. Which leads me to my next topic...

Cooling

As I said before, when you up the voltage to your CPU, the heat output great increases. This makes proper cooling a necessity. Here is a good set of links related to cooling and a few other topics.

There are basically three "levels" of case cooling:

Air Cooling (Fans)

Water Cooling (look here)

Peltier/Phase Change Cooling (VERY expensive and high end cooling)

I really don't have much knowledge on the Peltier/Phase Change method of cooling, so I won't address it. All you need to know is that it could cost you upwards of $1000 dollars and can keep your CPU at sub-zero temperatures. It's intended for VERY high end overclockers, and I assume that nobody here will be using it.

The other two, however, are much more affordable and realistic.

Everybody knows about air cooling. If you're on a computer now (and I don't know how you'd be seeing this if you're not ), you probably hear a constant humming coming from it. If you look in the back, you will see a fan. This fan is basically all that air cooling is: the use of fans to suck cold air in and push hot air out. There are various ways to set up your fans, but you generally want to have an equal amount of air being sucked in and pushed out. For more info, refer to the link that I gave at the beginning of this section.

Water cooling is more expensive and exotic than air cooling. It is basically the use of pumps and radiators to cool your system more effectively than air cooling. For more info on it, check out the link that I gave next to water cooling before.

Those are the two most commonly used methods of case cooling. Good case cooling, however, is not the only component necessary for a cool computer. The other main component is the CPU Heatsink/Fan, or HSF. The purpose of the HSF is to channel heat away from the CPU and into the case so that it can be pushed out from the case fans. It is necessary to have an HSF on your CPU at all times. Your CPU will be fried in a matter of seconds if it is not.

There are tons of HSF's out there. For a ton of info on HSF's and everything that goes with them, check out this page again. It basically covers all you need to know about HSF's and air cooling.

Critical Overclocking Programs You’ll Need

CPU-Z: General System Monitor and report.
ClockGen – optional: Make sure your get the version for your Chipset. This program allows you to Overclock from within windows. Not always as reliable as physically changing BIOS settings, but gives you an easy way to play with your settings without dozens of reboots.
Memtest86: You'll need to run this from a Floppy or Bootable CD. This basic program is still considered the best for testing your RAM
SuperPi: Intensive mathematical program that stresses CPU/Memory pretty extensively. I like this program because it gives you a good indication of your overclock in under a minute’s time.
Prime95: Clearly one of the best stability testers – used by all of the overclockers. It’s kinda old software, but it’s damn good.
MBM5 or SpeedFan: Monitor your temperatures, voltages while you’re in Windows or any OS. It’s one of the ‘must’ softwares. Why? Because you can not always reboot to see what are your temperatures, these aren’t always accurate, but they’re clearly better then nothing

Critical Components for a Quality Overclock

POWER SUPPLY (AMD & Intel)
Power Supplies are missed so often when it comes to figure out why your system isnt overclockig the way it should. DONT SKIMP HERE! Get yourself a quality Power Supply and you'll never regret it. The Power Supply that comes with most cases is garbage. If budget is tight, Go with an ANTEC or ENERMAX case. These usually come with a pretty decent supply. For detailed Power Supply Information, see DavidHammock's Power Supply Guide, Pandaking's Guide, theblackmages' Guide.

RAM (AMD & Intel)
A64s LOVE TCCD based ram. see Tim's TCCD Memory Guide for the best options.
There are several more factors that go into a quality and Stable A64 Overclock, that there are with Older XP
and Intel based systems. A few of the factors we need to take into Consideration are

CPU Multiplier (AMD & Intel)
All A64s are at least Half Locked. This means that you can set the CPU Multiplier Lower than
stock, but not Higher. This is a Good thing. Very rarely with A64's would you ever need to raise the CPU Multiplier over the Factory setting. The exception to this are the FX chips, they are fully unlocked.

CPU Voltage (AMD & Intel)
Most A64s have a default voltage of 1.4v to 1.6V. A64s are extremely efficient and usually can only take about 1.7v before they just start producing excess heat. I've run my Mobile up to 1.9v but found it did NOT help my overclocks and simply caused the CPU to produce enormous amounts of heat. These are NOT XP-M chips! While I doubt that running voltages between 1.75 and 1.9 will cause any permanent damage, it certainly has not shown to be beneficial in any tests I’ve seen so far.

HTT Frequency (AMD only)
A64s don’t use a traditional Front system Bus. Instead they use a HyperTransport. I can only assume its abbreviated "HTT" to differentiate between Intel’s "HT" and Hyper-Threading Technology. They are VERY different.

The HyperTransport is what controls the base frequency for communications and CPU speed in our A64 System.
The CPU Speed is controlled by the HTT Multiplied by the CPU Multiplier, The HyperTransport or Memory controller is controlled by the HTT Multiplied by the HTT Multiplier, and Memory speed is controlled by the HTT Frequency, Multiplied by the CPU Multiplier and then DIVIDED by the Memory Divider. That’s a bit confusing for most folks. And it took me a while to grasp the concept as well.

HTT Multiplier (AMD only)
Most AMD Motherboards are designed to handle an 800-1000 MHz Hyper Transport bus. Factory Default on 754 CPUs is 800 MHz (A 4X Multiplier) and 1Ghz (5x) on 939 CPU's this is a Critical part of Overclocking an A64 to the Max. Pushing the HyperTransport past 1Ghz can cause all kinds of system instability that is commonly misconceived as "I maxed out my CPU" or "My Ram is holding me back"

Memory Divider (AMD & Intel)
This is one of the most Confusing aspects of A64 Overclocking. There is ALWAYS a memory divider.
Setting the Memory to 1:1 means that the HTT bus is multiplied by the CPU Multiplier and then Divided by the CPU Multiplier to set the Memory speed. This means that it is OK to run your Memory at its peak efficiency and still go higher with your HTT bus if your CPU can take it. Take note that I said its "OK" not advisable. There are still sufficient tests out there showing that running a 1:1 ratio will garner you the best overall performance. I plan on adding a few test results in the next week or so showing the difference in performance using a higher memory divider than CPU Multiplier.

Since A64's use an On chip memory controller, the Ratio must be calculated a bit differently than old. 5:6 is NOT always 5:6. See that chart at the end of this post for a prety darn close representation of what each divieder is doing. Thanks to Oskar from DFI for the chart.

Memory Voltage (AMD & Intel)
Most motherboards offer a degree of memory voltage options. The memory of choice lately has been Samsung TCCD Based modules with Brainpower PCB's. These Modules run at 2.6v stock voltage, and can usually do no better with voltage up to about 2.8-2.9 volts. There have been a few reports of better settings with voltages over 3v, but these seem to be pretty rare
situations.

Most other memory can benefit from having additional voltage run through it. The king of this is the elusive Winbond BH-5 based memory modules. If you’re lucky enough to have some of these, you may want to invest in an OCZ Memory Voltage Booster if your motherboard is compatible as these can run some very impressive timings with a lot of voltage....
Speaking of Timings...

Memory Timings (AMD & Intel)
There are 5 Numbers in our Timings that we need to worry about a lot. Personally, I would like to learn more about the other numbers, but as of this writing, I'm pretty much in the dark there.
What we do need to worry about are CAS Latency, RAS to CAS Delay, RAS Precharge, and Cycle Time(Tras), and CPC (command Per Clock).
Ideally, we want these timings to be 2-2-2-5 1T. Most TCCD based module does this at 200 MHz (DDR400) and can usually go up to 215-220 with a Bump in Voltage to 2.7, and then we need to loosen them to go higher. 2.5-3-3-7 is still considered reasonable memory timings for an A64 system, and some people even go out to 3-4-4-8, but I would personally advise against using timings that high with an A64 System. We ALWAYS want to use CPC (1T) this means the Command per Clock interface is enabled. 2T performs extremely poorly on A64 systems. But since our memory controller is on the CPU, the Double Sided memory problem that plagues XP Motherboards is not evident. Give AMD a WOOT for that one.....

Chipset Voltage (AMD & Intel)
Usually just a small bump in Chipset Voltage will stabilize a flakey HTT bus. 1.6 is Stock on most motherboards, but 1.7 to 1.8 is acceptable as long as you have decent cooling on your Northbridge chip. Many A64 Motherboards use Passive heatsinks on these chips so before you install your dandy new A64 system, take off your NB Cooler and replace the Factory thermal past with some AS-5. This is usually enough to keep the MB Cool enough to run the extra voltage. Placing Ram Sinks on your Southbridge and any other heat producing chip is never a bad idea either.

AGP/PCI Lock (AMD & Intel)
The AGP and PCI Bus' are tied together on all motherboards that I know of. They are also derived from the FSB (Or HTT in the case of AMD) frequency by a divider. NVidia NForce chipsets have whats called a PCI/AGP Lock. This keeps your PCI and AGP Bus at a constant speed no matter what your HTT bus is. This is CRITICAL. If your PCI bus is too fast, you WILL corrupt hard drive data. If your AGP Bus is too fast, you WILL have Video problems. Via Chipsts have been known to have Faulty PCI locks. This appears to be corrected in the KT800 Pro Chipset, but KT800 and below SHOW a PCI Lock in most bios's but it doesnt do much... This is a Primary reason why overclockers stay away from these boards.
On your Nforce or Via KT800Pro board you want this setting at 33Mhz if its listed as a PCI lock, or 66-67Mhz if its listed as a AGP Lock. Pushing this offers absolutely no benefit as the bandwidth provided by these frequencies is more than todays Hard Drives or AGP Video cards can use.

COOL N' QUIET (AMD only)
Disable this. This is a feature that will automatically UNDERCLOCK your system if it feels it doesnt need to run so fast... Who are "They" to tell us how fast out CPU should run?

Troubleshooting an Overclocked system

Many people want to overclock their computer in one big jump so they dont have to mess with it. If you dont have patience, don’t overclock! It takes time and you have to try different things to accomplish it a lot of times.

1) Make sure you have a good bios. Try flashing to another one and see if its any better than the one you have. The latest is not always the greatest, and a good bios may not be good on your system.
2) Make sure you are running the latest chipset drivers for your motherboard.
3) Make sure you have sufficient temperatures to overclock with. If your running temps at 50C or over idle, dont bother with overclocking until you get better cooling.
4) Make sure you have a GOOD quality Power supply and watch your voltage rails. If they flunctuate too much replace it, because it will limit you stability and overclocking ability.
5) Make sure your memory can handle the overclock that you want to achieve.
6) For overclocking start your Vdimm voltage at 2.8v (if your mobo maxes out at 2.7 then set it there).

Now thats the basic things to look for if you cant get very good overclocking out of your system.

Example: Your system locks up and/or reboots all the time
Answer: This means your system is not stable. Could be several reasons. First try to raise your vcore by a small amount if you have enough temperature headroom. If you raise the vcore and it still happens, try loosening the ram timings and try again. If you cannot get your system stable than reduce your overclock by a small margin and try again. Many times a 3-5 Mhz FSB decrease will make it stable. Check for stability with a program like Prime95 and let it run for a minimum of an hour. (most people test for 12-24hrs) If it runs without freezing or locking up, your good to go.

Also a major reason for this problem is the lact of Rail voltages. Check your rails using MBM5 or similiar and compare them with the BIOS reading. If they are okay when system is Idle that dont mean your PSU is okay. Run prime95 and check your voltages with a voltmeter. Now run a graphic intensive application (3dmark03 or similiar), and check them again. The voltages should be in the limits below.

Rail: +5V: ~4% (+4,8V ~ +5,2V)
Rail: -5V: ~10% (-4,5V ~ -5,5V)
Rail: +12V: ~5% (+11,4V ~ +12,6V)
Rail: -12V: ~10% (-10,8V ~ -13,2V)
Rail: +3,3V: ~4% (+3,15V ~ +3,45V)

The following are the most common arrangements of ATX mobo connectors. Not all manufacturers follow the coloring below but most do. The number is the respective pin # on the connector.
1. Power Good * - Orange
2. +5Vdc - Red
3. +12Vdc - Yellow
4. -12Vdc - Blue
5. Ground - Black
6. Ground - Black

7. Ground - Black
8. Ground - Black
9. -5Vdc - White
10. +5Vdc - Red
11. +5Vdc - Red
12. +5Vdc – Red

Example: Your games or benchmarks crash to desktop
Answer: Most notably the cause of this is your overclock is too high. Most of the time its the overall speed and not just a multi or FSB issue. Reduce the overall clock speed by reducing the FSB by 5Mhz and try again. Keep going until your games run smooth without crashing.

Example: Your temperatures are too high
Answer: Simple your cooling is not doing its job. There are several possible fixes.
1) Remove your heatsink and reseat it using AS5 (arctic Silver 5 preferred – it’s one of the best thermal compounds currently one the market) or similiar thermal Grease. Following all directions for applying the Thermal Grease evenly and smoothly. Application instructions
2) You might just have more wattage than your HS/Fan (or waterblock) can keep cool. If this is the case after reseating you still cannot bring temperatures down, than reduce the vcore voltage. You will probably have to reduce the overclock as well when dropping voltage.

Example: Your system will not boot up
Answer: If your system will not boot up after adjusting your bios, then turn the power off, unplug the system, and (a) use the clear CMOS jumper (b) remove the CMOS battery for about 1 minute. If you use the jumper put it back to normal operation or put the battery back in, plug the PSU in and start the computer. Go into your bios and set it up again. This is a common practice when overclocking, so get used to where your CMOS jumper is for when you need it.

Example: your system will not boot up after clearing CMOS
Answer: If you clear CMOS and system still will not boot up then you have to narrow down what the problem is. This is where having extra parts or a good friend will help out:
1) confirm that you have power coming from your PSU is the first thing. If your fans come on and optical/hard drives spin than most likely your PSU is not the problem (Sometimes it still can be at this point)
2) remove the memory one stick at a time and retry. If you only have one stick remove it and see if the mobo beeps when trying to boot. If it dont beep than its not the memory most likely so put it back in.
3) remove any PCI expansion cards that you have installed. Try to boot the machine. If nothing still leave the PCI cards out anyway.
4) unhook your hdrive and optical drives from the motherboard and try again. It will still boot up without harddrive being attached so dont worry about that.
5) Remove your video card and try another one. If you dont have another one try booting up. If it beeps than it could be your video card, you need to get another one and try it. If you dont have a friend that has one to borrow or an extra one laying around then go to your local department store and buy one try it and if it still dont work take it back.
6) Now if you still have trouble you have eliminated everything except motherboard and CPU. Most of the time (not always) it will be the motherboard IF you havent ran your CPU with excessive temperatures. If you have another CPU replace it and see if it boots up. If you dont have another one, your gonna have to buy one or put yours in another system to test out. If it works in another system you know your motherboard has bit the bullet. buy a new one.

Example: Your system just beeps when turning it on
Answer: There are several things that could cause this. Most of them are listed above but the first thing to do is try to reset the CMOS. High FSB will cause this sometimes when the memory will not run at the set speed. If you reset the CMOS and still nothing happens make sure all your cables are connected properly and all Memory and PCI/AGP cards are intalled into their sockets all the way. The easiest way is to remove them and put them back in.

Grounding problems can cause temendous hair loss when you pull it all out because you have tried everything and nothing works. lol If your motherboard is grounded to your case at any point, most of the time it will not boot up. Make sure that you motherboard is not touching any part of the inside of the case. A secure thing to do is use the felt or cardboard washers when installing your mobo in your case. This will help eliminate some of these problems.

Example: System dont boot up after adjusting FSB
Answer: Simple solution, Clear you CMOS and restart again. Go into the bios and set everything again. Its a good idea to write down things when you change them so if this happens you know where you were and can set the settings accordingly.

Example: System dont boot after flashing bios
Answer: This is a common pain and sometimes happens for no reason. (Speaking from experience) If you have this problem you better have another bios chip for your motherboard. You can hot swap the bios chip and flash your corrupted chip only if you have another chip for your motherboard. Its a good idea to keep a spare.
1) Download this (hot swap bios chip (thanks Madramper for this link)) and prepare you floppy disk with these files.
2) Now reboot your machine and put the floppy disk that you made in the floppy drive (Hopefully you have one, If not prepare a bootable CD-ROM and add these files to it. Sometimes it works and sometimes it dont) and boot up.
3) The program will tell you when to swap bios chips follow directions and your bios chip is now programmed, hopefully if all goes well.

Example: System freezes or shuts down and will not start back up
Answer: Most of the time the cause of this is a failed Power Supply. The first thing to try is check your power supply with a volt meter to see if its putting out any current. Even if it is though, that dont mean that you have a good power supply. Try another power supply first to fix your problem. If a new power supply does not fix your problem than refer to the steps above in the : Example: your system will not boot up after clearing CMOS

Example: You finish assembling your new system and it wont start
Answer: 1. Verify that you have the power supply plugged into a wall outlet, PSU turned on, and connected to the Motherboard.
2. Check the Clear CMOS jumper to verify that it is in normal mode and not Clear. (Check Motherboard manual for location)
3. Verify that fans are running and drives spinning. If neither of these occure you Power supply is not supplying voltage to the components.
4. If fans are running and drives spinning, a notable cause of this problem with a newly built system is shorting. Remove your motherboard from its case and lay it on a non-conductive piece of material. Attach your video card and power cables, memory. you will have to have the mobo close enough to your case to use the Front panel headers from your case. Connect these headers to their proper location on the Motherboard. Connect your power supply and turn it on. If your system starts now (*see footnote), you had a short somewhere. Reinstall the mobo in your case making sure that its not touching the case anywhere, and hook everything up. It should work now, if not you still have a short.

**~~Overclocking FAQ~~**

This is just a compilation of basic hints/tips for overclocking, and a basic overview of what it is and what it involves. PM me if you have an addition or a correction, and I'll mention you if I use it.

How well will X overclock?
Not all chips/components overclock the same. Just because ‘Bobby’ got his Prescott to 5ghz, it doesn't mean yours is guaranteed to do 4ghz. And the like. Each chip is unique in it's overclockability. Some are great, some are duds, most are average (well, duh!). Try it and see. Whether or not you keep it if you get a dud is up to you and your store's return policy.

Is this a good overclock?
Are you happy with what you got? If so, then sure (unless it is just a 5% or less overclock - then you need to keep going unless it becomes unstable after that ). Otherwise, keep going. If you're at the limit of your chip, then you are at the limit of your chip. Nothing else you can do.


How hot is too hot/How much voltage is too much?
This is a very good reference for this type of thing.
Look there before asking questions about this here. As a general guideline for safe temperatures, temps at full load should be at or below 60C for a P4 and 55C for Athlons. Lower is better, but don't freak if your temps are high. Check the resource, and see if it is well within specifications (as it likely is). For voltages, 1.65-1.7 is a good limit for a P4 and an Athlon can go up to 1.8 on air/2.0 on water - generally speaking. Depending on cooling, more voltage/less voltage may be appropriate. The limits on chips are surprisingly high. For example, the maximum temperature/voltage on a Barton core Athlon XP+ is 85C and 2.0 volts. 2 volts is plenty for most overclocks, and 85C is rather high.

Do I need better cooling?
Depends on what your current temperatures are and what you're planning to do with your system. If your temperatures are too high, then you probably need better cooling, or at least need to reseat your heatsink and work on cable management. Good cable management can do wonders for case airflow. Also, proper application of thermal paste is very important for temps. Use the guide from the TIM(Thermal Interface Material) manufacturer and follow it as closely as you can. If that doesn't help enough or at all, than you probably need better cooling. But see the above section and included link before you start complaining about your temperatures. We don't really want to hear it, unless they are spectacularly bad (or good). Then again, most of those instances can be chalked up to inaccurate temperature sensors on the motherboard. So don't post these questions unless you really can't figure it out and you have tried a few things already.

What are the common methods of cooling?
The most common method is air cooling. This involves putting a fan on top of a heatsink which is then placed on top of the CPU. These can be either very quiet, very loud, or somewhere in between, based on the fan used. They can be fairly effective coolers, but there are more effective cooling solutions. One of these is watercooling, but I'll get into that in a bit.

Air coolers are made by companies such as Zalman, Thermalright, Thermaltake, Swiftech, Alpha, Coolermaster, Vantec, etc. Zalman makes some of the best quiet cooling units and is known for their "flower cooler" design. They have one of the most effective quiet cooling designs in the 7000Cu/AlCu (all copper or aluminum and copper construction) and it is also one of the better performing designs. Thermalright is (quite) arguably the producer of the highest performing heatsinks when used with appropriate fans. Swiftech and Alpha were the performance kings before Thermalright came into the spotlight and are still excellent heatsinks and can be used in more applications than the Thermalright heatsinks because they are generally smaller than the Thermalright heatsinks and so fit on more motherboards. Thermaltake produces an abundance of cheap heatsinks, but they aren't really worth it IMHO. They don't perform on the same level as the other heatsink manufacturers' heatsinks, but they can be used in a pinch or in a budget box. That covers the most popular heatsink manufacturers.

On to watercooling. Watercooling is still mainly a fringe movement, but it is becoming more mainstream all the time. NEC and HP (I believe) make watercooled systems that can be bought retail. Still, most of watercooling is in the enthusiast area. There are several components involved in a watercooling loop, even the most basic one. There is at least one waterblock, usually on the CPU and sometimes the GPU. There is a pump and sometimes a reservoir. There is also a radiator or two.

The waterblocks are generally constructed from copper or (less commonly) aluminum. Even less common, but becoming more so, is waterblocks made of silver. Danger Den makes the S-TDX, and it is possible to procure a silver Cascade block. There are several different kinds of internal designs for waterblocks, but I won't get into those here. Visit the watercooling sub forum to learn more. The pump is responsible for pushing water through the loop. The most common pumps are Eheim pumps (1046, 1048, 1250), Hydor (L20/L30), and the Danner Mag3. Iwaki pumps are also popular among the high-end crowd. The Swiftech MCP600 pump is becoming more popular, as is the Liang D4. Both of those are high-head 12V pumps. A reservoir is helpful because it adds to the volume of the water in the loop and makes filling and bleeding (getting the air bubbles out of the loop) and maintenance easier. However, it takes up a good deal of space in most cases (a small reservoir isn't much good) and it is just one more thing that could leak. The radiator can either be a retail one, such as Swiftech's radiators or the Black Ice radiators, or made from a heatercore from a car. The heatercores generally offer superior performance as well as a lower price tag, but are also harder to assemble, as they usually don't come in a form that can be adopted to watercooling quickly or easily. Oil coolers are an alternative for those with strange size requirements, as they come in a great variety of shapes and sizes (well, usually a rectangle). However, they don't perform quite as well as a heatercore. Again, look at the watercooling sub forum for more info. The tubing is also a factor in performance. Generally, 1/2" ID is considered to be the best for high performance. However, 3/8" and even 1/4" ID setups are becoming more common, and their performance is also getting closer to that of a 1/2" ID loop. That's about it for watercooling in this section.

What are some of the less common cooling types?
Phase change, chilled water, peltier (TEC), and submersion setups are less common, but higher performance, cooling alternatives to those listed above. Ask in the extreme cooling sub forum about any of these methods. Read up on any of these before you use them. Peltier cooling and chilled water loops are both based on watercooling, in that they are based on a modified watercooling loop. Peltier is the most common of these types. A peltier is a device that, when current is applied, gets hot on one side and cold on the other. This can be used between a CPU and a waterblock or a GPU and a waterblock. Less common is peltier cooled northbridges, but this isn't really necessary. Ever. A chilled water loop uses either a peltier or phase change to cool off the water in the loop, usually replacing the radiator in the loop cooling the CPU/GPU. Using a peltier to do this is not very effective, because it often requires another watercooling loop to cool it off. The peltier is generally sandwiched between either a heatsink and a waterblock or a waterblock and another waterblock. The phase change method involves placing the cooling head or cooling component from an A/C unit or the like in a reservoir. Antifreeze is usually added to the water in about a 50/50 ratio in chilled water setups, because freezing isn't good. The tubing has to be insulated as do the blocks if sub ambient temperatures are ever reached in case of condensation. Phase change involves a compressor and a cooling head attached to the CPU or sometimes the GPU. I won't go into much depth about it here. Other less common methods involve dry ice, liquid nitrogen, watercooling the PSU and hard drives, and other things like that. Using the case as a heatsink has also been considered and done as well.

I just thought up a cool idea for cooling, is it original?
Is it listed up above? If so, then no. Also, the search function is a wonderful thing now that it works.

What about prebuilt watercooling units?
The Koolance one and the Corsair one are the only ones really worth considering. The little Globalwin one is alright, but no better than any half-decent air cooling. The rest are no better. Avoid them. The newest Thermaltake one may be alright, but see the above warning about Thermaltake products. New kits may be decent (The kingwin one seems to be so) but read multiple reviews and at least one that tests it on the platform you will be using before buying anything.

What are the dangers of overclocking?
There are several dangers attached to overclocking, and they should definitely not be overlooked. Running any component out of spec will shorten its lifespan; though newer chips are able to deal with this far better than older ones, so this is less of a problem than it used to be, especially if you upgrade every 6 months or every year. For long term stability, IE computers that are going to be running for more than 2 years or so with a load most of the time, overclocking is not a good idea. Also, there is the possibility that overclocking will corrupt data, so if you don't do backups of any data you care about, overclocking is not really for you (and you should really start doing backups anyway) unless you can easily replicate the data and it will not cause any problems. But take possible data loss into account BEFORE you start overclocking. You will thank yourself for doing this if anything goes wrong. Overclocking (especially large overclocks at a high voltage) is not recommended if you only have one computer and you need it for anything important, as the possibility of component failure is quite real (I have lost a few components to overclocking, but not as many as some have lost) so that needs to be taken into account as well. On a lighter note, addiction and "Empty Wallet Syndrome" are also very real risks to overclocking . Be careful of those.

What limits my overclock?
Generally, the RAM and CPU are the only significant limiting factors, especially in AMD systems because of the problems inherent in running the memory asynchronously (see the FSB section down below) The RAM has to run at the same speed as the FSB or at a fraction of it. Complex fractions are allowed, meaning the memory can be run at a higher rate than the FSB, not just a lower one. With the option to run looser timings/more voltage through memory, though, it is becoming less and less the limiting factor, especially since newer platforms (P4 and A64) suffer less of a performance hit from running async. (again, see below) The CPU has become the main limiting factor. The only way to deal with a CPU that doesn't want to run any faster is to pump more voltage through it, though exceeding the maximum core voltage shortens the life of the chip (though overclocking does this as well) but sufficient cooling stems this problem. Another problem with running too high of a core voltage manifested itself on the P4 platform in the form of SNDS, or Sudden Northwood Death Syndrome, wherein running any voltage over something like 1.7 (not sure of the exact number, no one is) would result in the quick and untimely death of the processor, even with phase change cooling. However, the newer 'C' core chips, the EE chips, and the Prescott chips have not had this problem, at least not to nearly the same extent. The cooling can also prevent a good overclock, as having temps that are too high can lead to instability. But if your system is stable, then the temps usually are not too high.

Now that I've overclocked a lot, what should I do?
Run some benchmarks if you want to. Run Prime95 (Or your stress test of choice - it is up to you) for a sufficient time period (Usually 24 hours straight is considered a stable system)
/Begin shameless F@H plug
Then install Folding@Home if you haven't already.
/End shameless F@H plug
That covers the basic aspects of overclocking. The questions from this point on are the more technically involved sections.

Why does running the PCI/AGP bus out of spec cause instability?
Running the PCI bus out of spec causes instability mainly because it forces components with very strict tolerances to run at a different frequency then they are intended to. The PCI spec is usually stated at 33mhz. Sometimes it is stated at 33.3mhz, which I believe is closer to the real spec. The main victim of high PCI speeds is the hard drive controller. Certain controller cards have a higher tolerance than others, and so are able to run at increased speeds without noticeable corruption. However, the onboard controllers on most motherboards (especially SATA controllers) are extremely sensitive to high PCI speeds, and can have corruption and data loss if the PCI bus is running at even 35mhz. Most are able to do 34mhz, as it is really less then 1mhz out of spec (depending on where the motherboard stops rounding to 34mhz... for example, most motherboards will probably report any FSB from 134mhz-137 as being a 34mhz PCI speed. The actual range is from 33.5mhz to 34.25mhz, and may vary even more based on variations in the clock frequency of the motherboard. At higher FSBs and higher dividers, the range can be even more). Audio and other integrated peripherals also suffer when the PCI bus is run out of spec. ATI video cards are a lot less tolerant to high AGP speeds (directly related to PCI speed) than nVidia cards. With that in mind, most Realtek lan cards (the PCI based ones that occupy an expansion slot) are rated for safe operation at anywhere from 30-40mhz.

Intel Prescott and Northwood tweak to utilize L2 cache (thanks Maurice )
Maurice did this for his m0, and he did it with my presscot. He used 1024kb of cache. He noticed that his memory scores went up a bit and system seemed finer tuned.

instructions:
RUN>type REGEDIT>Hkey local machine>system>currentControll set>Control>Session Manager>Memory Management
Right-click SecondLevelDataCache, click modify, click on decimal and the then type in 1024 for presscots, 512 for northies.

AMD64 Processor Voltage Guidelines with chart:

This guide is designed to give everyone a good idea of the voltages you can run on your A64 CPU’s.
Unfortunately, this chart is based on Observation and personal experience. There is ALWAYS a risk when playing with CPU Voltages. If you Blow your CPU up in the “SAFE” range, IT’S YOUR FAULT. If you cannot accept the Risks of Overclocking, then DON’T DO IT.



See Athlon64 Guide from Wiki. It’s an awesome guide, if you have got an A64 you shouldn’t miss that guide.

Couple of interesting guides from DevArticles

Sempron Overclocking by DMOS
P4 800MHz FSB Overclocking by DMOS
Unlocking an AthlonXP by Memphist0
Applying Thermal Paste by SpeeD
MADSHRIMPS' "AMD Overclocking Guide"

Final words...

I hope that I have done my job of collecting the clearest screen shots, and information about overclocking, covering every part of it.

So I can't stress enough, that this is definitely NOT my guide, these aren't my photos, my guides, my FAQs, these are from the NET, other forums (EOC – extremeoverclocking.com), and kinda stuff, and I just collected the large number of information available about OC over the net, and put them together in one place, at this thread.

Sources used for this OC Ultimate Guide

Thanks, and congrats to those people who're capable of making these guides – they invested a large amount of their time, so they deserve all of our respect.

Direct-link to the REAL guides:

Jarad's Overclocking Guide
DMOS' P4 Overclocking Guide (@DevH)
skeensp's "Troubleshooting your overclocked system" (@EOC)
MADSHRIMPS' "AMD Overclocking Guide" (@www.madshrimps.be)
Impaqt's "The Somewhat Complete AMD64 Overclocking" (@EOC)
Bigmoose's AMD Overclocking Guide" (@EOC)

Good luck, and enjoy your newly overclocked system.

Also visit our Benchmarking Section -- and post your scores. Have fun!

Introduction

Let me explain why I decided to write an article about stability testing. A few days ago I've been at one of my friend's place. He is also an overclocker, so as you all imagine, he is not running his rig at stock. Nevermind the details about system specs and frequencies. He's downloading some torrents, folding in background, surfing the web, chatting on Yahoo messenger, winamp running- because we're listening music, and also burning a DVD for me. All of these applications running at the same time, no problems, multitasking is an awesome invention. The DVD burning was almost complete, when boom, BSOD. You can imagine my reply: "What the hell? You aren't stable?" He explains that he's running his rig at these speeds for a few days already, and that he tested with games, while folding. Well- see? That's not enough. It was unstable, and needed to increment the vcore with a little tick to fix the problem. Of course some people may say, that it wasn't a big problem, only a BSOD (Blue Screen Of Death). Well, that's true. But personally I like to know that my rig is _always_ stable, and that I know whenever what I'm doing it won't crash. Think about it... it's an awesome feeling when you're totally sure that your car won't crash, when you're going to a long trip across Europe with your fiancée. Am I right? It's the same with computers.

Some people tend to run their system at unstable overclock, because they just don't care. They overclock their system for only one reason- to be the best and/or to prove something. They OC to an unstable but high enough speed, benchmark it, make screenies, and then post 'em on the forum, and then ~omfg wtf pwned~- maybe some people think that they're doing good, but in my opinion that's bad. People should only overclock if they aren't satisfied with their current system overall performance (for example lagging due to low FPS at your MMORPG, or you hate the huge compilation and/or rendering time, when working, encoding or designing). Otherwise there's no reason.

My goal with this article will be, that every overclocker who reads it, will know how much stability means, and it's worth that their system to be at stable configuration- and how to test it, how to make sure that it's stable or not.

Stability? Why should I care about it?

Your computer is a tool, made to aid you in performing a variety of tasks, whether it's playing your favoruite MMORPG- while raiding with other 40 people, burning a DVD, or writing up your twenty page Philosophy term paper.

When your computer is running, it's stressing itself- it's usually working pretty hard, how much depending of course on what you're doing with it. Your tool is seeing some use- as a hammer gets bashed and swung, your computer is performing all kinds of processes. If your hardware is unstable, it's bound to make a mistake sooner or later - your very expensive hammer is going to either crack, or fall apart and hit you in the face.

Without trying to scare anyone- that mistake could happen while you're defragmenting your hard-drive, or it could happen just as you're saving that previously mentioned twenty page philosophy term paper on Post-Modern Existentialism that you've been slaving over for the last month (I hope you backed it up).

That little mistake could cost you everything on your hard-drive. That's bad, and scary, isn't it? Think about it...

In short, if your computer hasn't been stability tested, it's entirely possible that it isn't stable, and is going to mess up on you at just the wrong moment. It’s Murphy’s Law, and it happens all too often for my liking.

If you’re still not impressed, go to your local store, and spend lots of money on a tool. Then do something to it so it doesn’t work properly. This tool is your computer.

"Today's computers are not perfect. Even brand new systems from major manufacturers can have hidden flaws. If any of several key components such as CPU, memory, cooling, etc. are not up to spec, it can lead to incorrect calculations and/or unexplained system crashes.

Overclocking is the practice of increasing the speed of the CPU and/or memory to make a machine faster at little cost. Typically, overclocking involves pushing a machine past its limits and then backing off just a little bit.

For these reasons, both non-overclockers and overclockers need programs that test the stability of their computers. This is done by running programs that put a heavy load on the computer. Though not originally designed for this purpose, this program is one of a few programs that are excellent at stress testing a computer." from Prime95's Help File- 'stress.txt'

Overclocking- and how it affects Stability

Stability isn’t just important for us overclockers, it’s important for people who use stock hardware as well. However, we overclockers are at far greater risk because of what we do to our hardware.

When we overclock, we push the limits of how fast our hardware can run- we add strain to our hardware in everyday use, and we drastically increase the chances of having an unstable setup, even if everything looks peachy on the surface (or desktop if you will).

Almost all of us have had some experience with instability: trying for that extra speed step, and getting a reboot, or getting artifacting after clocking up our video card. On the surface, more voltage, less speed, or better cooling makes the problem go away. But underneath the underneath, a potential for instability still exists- you can never be sure just how solid your setup is until you’ve tested it thoroughly and properly.

This potential for instability is a very important concept that many of us disregard – many people are of the mindset that if it looks O.K. on the surface, and if it runs O.K. for the odd light gaming or benching session, then it probably is O.K.

This mentality is nicely comparable to that of someone looking at quicksand – quicksand looks solid on the surface (surface = desktop). Unknown to the observer however, quicksand is all mushy, to some degree, underneath the surface (underneath = a processor doing some complex math). The dangerous quicksand and the perfectly safe sand-by-the-beach both look the same from a surface perspective.

"Why run a stress test if you are going to ignore the results?" These people want a guaranteed 100% rock solid machine. Passing these stability tests gives them the ability to run CPU intensive programs with confidence." from Prime95's Help File 'stress.txt'.

Every overclocker should take a little bit of time, and test their machine thoroughly. In the next section I’ll deal in-depth with some effective stabilitytesting methods. Read on.

Proper Stability Testing- how to do it?

To be perfectly honest with everyone, stability testing isn’t all that complicated.

Awareness is way more than half the battle.

There are three programs which I live by when it comes to stability testing, two more so than the third, but I digress.

These three programs are Prime95, 3DMark 2001 SE, and memtest86. All three are small programs that are completely free and easily accessible to anyone running a Windows machine (prime95 & memtest are also available on linux) with internet access (click on their names to go to the download link).

There are also tons of ‘lesser’ (my label for them) stress testing programs which are effective to varying degrees – when it comes to these it’s all about using what you feel is necessary, credible, and thorough. Some of the many stress testing programs I’m not going to mention or talk about are fairly effective substitutes for the ones which I am going to talk about.

However, if you skip any of the "big three", you really aren’t being thorough enough, to put it bluntly. All three do need to be used, individually they are inconclusive.

One important thing for you to remember is that this is not an opinion. This is a fact that is backed up by a lot of experience, most of which isn’t mine- rather that of the millions of other overclockers out there.

We’ll do this part in three steps.

STEP 1: CPU STABILITY - PRIME95

There is one program that is very widely viewed as the CPU stability-tester to rule over all CPU stability testers, for good reason, and that program is Prime95.

Please keep in mind that Prime95 can error even with a completely stable processor overclock. Unstable memory, or other system problems can also cause erroring in Prime95 - your processor is not the sole potential cause of Prime95 testing errors.
"This program is a good stress test for the CPU, memory, caches, CPU cooling, and case cooling. The torture test runs continuously, comparing your computer's results to results that are known to be correct. Any mismatch and you've got a problem!" from Prime95's Help File 'stress.txt'.

Prime95 puts your processor through a very rigorous "math test", and immediately checks your chip’s answers for any mistakes.

The work which Prime95 makes your chip do will bring your processor up to a near-peak load temperature, which in turn helps stress your processor as much as possible, while also conveniently giving you an idea of what your load temperatures are. Any potential for instability that’s present will be found by Prime95 after a sufficient amount of time, given that you use the software properly.

You can download the latest version of Prime95
here.

HOW TO USE PRIME95 EFFECTIVELY

First, install the program as you would any other. Next, run it, and go to the ‘Advanced’ tab – select ‘Password’. Type in the password 9876 and enter it. Now go back to the ‘Advanced’ tab, and select ‘Priority’. Set the priority level to 10.

This effectively gives all of your system resources to Prime95 when it is running – now any processes running hidden in the background won’t be able to steal work time from Prime95, ensuring the most effective stress test possible.

Here is a picture to clarify Priority Ten setup for Prime95.


When you want to stress test your processor, run Prime95, go to the ‘Options’ tab, and select ‘Torture Test’. Run the Torture test at the default settings. See the screenshot above:



Make sure that you have turned off any screensavers, and closed all other applications when Prime95 is running (close services like apache, ftp, Folding @ Home, Seti @ Home- any other background service).

Prime95 should never be run in tandem with any other stress testing programs, period. Prime95 is known and proven to be most effective when run by itself, and is less thorough when used with something else running at the same time. If you use Motherboard Monitor Five (aka MBM 5) to monitor your temperatures, you should turn the interval time way down – 60 seconds is appropriate.

If you have an Intel processor with Hyper Threading and/or any Dual Core processors, you need to run two instances of Prime95 for complete effectiveness (as a note for dual core HT processors, you need quad prime95 testing, that means 4 instances, 2 for each core, due to HT per every core). This is proven fact- in that two instances of Prime95 will catch instability that one instance won’t, on an Intel machine with HT. In order to run two instances simultaneously, simply install a second copy of Prime95 in a different folder, and run it in tandem with your original. Priority ten should be used for both instances of Prime95 in this case.

When you are stability testing with Prime95, you want to run the Torture Test for at least 24 hours. Why 24 hours?

There is a very common misconception that if your machine can pass Prime95 stability testing for, say, four hours, your machine will be able to run stable, regardless of what you are doing, for four hours as well, without issue. This is simply not the case.

Prime95 often finds errors in its 16th - 20th hour of testing, a potential for instability that wasn’t found after only four hours of testing. After only four hours of Prime95, the potential for instability still exists. 24 hours is widely viewed as a sufficient time period to catch any instability that may be present, but by all means test longer if you are able.

If 24 hours seems like an extraordinarily long time to leave your computer on, keeping your machine unusable because of the processes it’s doing, try running Prime95 overnight, and then through to all day while you’re at school or work.

For CPU specific testing, a Large FFT Prime95 test is an alternative to the more "system-stress" oriented Blend test that runs by default. The choice is ultimately up to the end user - the Blend test is recomended in these guidelines because of it's qualities as both a processor and system stress test.

That’s all there is to Prime95 – 24 hours of Prime95 at Priority 10 is "certified stable", and ready to rock for 24/7 use.

EXCELLENT PROCESSOR STRESS TESTING ALTERNATIVES

Distributed computing

A lot of people run distributed computing programs 24/7, which constantly keep their CPU at full stress load while helping to aid important scientific research.

Running a program like Folding@Home or SETI after passing 24 hours of Prime95 is a superb way to constantly keep an eye on your system's stability, while also aiding Medical research, or the search for extraterrestrial life.

It is imperative that one does not run a distributed computing program on a machine that hasn't been stability tested, as mistake-filled results do not in any way help the effort.

For more detailed information about these distributed computing programs, check out the ocforums SETI and F@H team forums.

F@H team forums: DevFolding

StressCPU

A new program called StressCPU, based on the Gromacs core (F@H) and designed for CPU stability testing, is a promising alternative to Prime95. The Gromacs core is known to be very stressful on an overclock, this program looks to have a lot of potential.

StressCPU can be downloaded here: link.

StressCPU has not been widely tested as of yet - I will add more information here as we learn just how thorough this application is for our purposes.

SuperPi

SuperPi, a Pi calcation program, is another excellent and widely proven CPU stess tester. The '32M' length benchmark is an easy-to-use indication of stability, and is usually quite accurate. A SuperPi software mod that can be looped indefinitely is in the works - such a program will be ideal for long-term processor stability testing.

SupePi can be downloaded: link.

OCCT

This program is really amazing. Made by a group French overclockers, with the intention of being an enthusiast-oriented stress-tester, OCCT is perhaps the very future of processor stability testing. This program is extremely effective - it will peak your processor temperature at a full workload, and in a relatively (compared to Prime95) brief period of time give a very thorough indication of processor stability.

OCCT can be downloaded here: link.

Toast

Toast is a temperarure-increasing processor stress tester that will take your chip right up to a peak load temperature and keep it there. Toast is a good indication of long-term stability, and excellent for testing the capacity of one's cooling.

Toast is available here: link.

STEP 2: 3D STABILITY – 3DMARK 2001 SE

When it comes to stability, 3D testing is often overlooked completely. Many people do not overclock their video cards, and as such decide that 3D stability tests are a waste of their time. They couldn’t be more wrong! An increasingly common phenomenon is an overclock which will pass Prime95 and memtest86 for 24 hours, but lock or crash 3DMark in a few minutes – it is for this reason that 3DMark testing is a good idea. And for those who do overclock their video cards, 3DMark is an invaluable video card stability testing tool.

"3DMark2001 SE is a diagnostics tool for measuring the 3D game performance of PCs. It is entertaining and easy to use, which makes it "must have" software for all home PC users interested in 3D games. Even a beginner PC user can get a game performance measurement with 3DMark2001 SE. For the more advanced users, 3DMark2001 SE offers a wide range of display settings and testing options for the benchmark run." from 3DMark01SE's Readme

You can download 3DMark 2001 SE here: link.

HOW TO USE 3DMARK 2001 SE EFFECTIVELY

Using 3DMark as an effective stability test is a little bit different from using it to bench your machine. There are two main ways to use 3DMark as a stability tester. Running all of the tests looped in order to test your entire machine, and running only the Nature test looped while checking visually for artifacting in order to test your video card at peak load temperatures.

After installing 3DMark, run the program, and select all the tests for use. Now click on the ‘Change’ button in the options section, and click the ‘looping’ box. See the screenshot above.





Next press CTRL+ALT+DELETE, and go to the Task Manager. Right-Click on 3DMark 2001 SE in the ‘applications’ tray, and select ‘Go To Process’. Right click on the process you are taken to, and select ‘Set Priority’. Set the Priority to ‘Realtime’. This needs to be done every time you use 3DMark. See the screenshot:



This effectively gives all of your system resources to 3DMark when it is running – any processes running in the background won’t steal resources from 3DMark while it’s stress testing, ensuring the most thorough test possible.

Make sure any screensavers are turned off, and that no other applications are running, and start running the tests when you’re ready.

You should always run 3DMark by itself, never at the same time as any other stress testers. This ensures that it’s doing the most thorough job that it can.

Because 3DMark will almost always lock within the first ten test run loops, if it’s going to lock at all, 4 hours of looped testing is a more than sufficient test for your machine. After four hours of looped testing, 3DMark has done all it really can, and isn’t going to catch any instability.

"An increasingly common phenomenon is an overclock which will pass Prime95 and memtest86 for 24 hours, but lock or crash 3DMark 2001 SE in a few minutes – it is for this reason that 3DMark testing is a good idea." from Readme.

The reverse is also often true- many machines can run 3DMark for hours and hours without issue, but will fail Prime95 or memtest86 after a short period of time; 3DMark isn’t particularly useful as a system stability test when used by itself.

For video card artifact stability testing, the 3DMark01SE Nature test (test #4) is about as good as it gets. The 3DMark01SE Nature test puts a lot of strain on your video card, and will get your card’s RAM and core up to a peak load temperature - the 3DMark01SE Nature test gets your GPU and Graphics RAM hotter than anything else will. When running the Nature test looped, for use as an artifact tester, one needs to visually keep an eye open for artifacting, as there is no built-in detection. Many find that the best way to do this is to pick a specific part of the test, and pay close attention to it – making any irregularities easily noticed. An hour of such testing with a periodic check for any artifacting is usually sufficient, although it's a very good idea to do a few runs of all the game tests afterwards as well.

Artifacting, or 'snow', is a term for visual erroring, almost always caused by graphics card instability. Artifacting most commonly makes itself apparant through large geometric objects flickering in and out on your screen, texture corruption (checker boarding), and 'texture snow', which appears as many white specks.

Other tests in newer versions of 3DMark can also be very effectively used to detect artifacting and video card instabilty, although the 3DMark 2001 SE Nature test is still the best at getting your video card's core and RAM temperatures to a peak.

You can download 3DMark 2003 here: link
You can download 3DMark 2005 here: link
You can download 3DMark 2006 here: link

STEP 3: MEMORY STABILITY – MEMTEST86 / MEMTEST86+

Memory instability is perhaps the stability-aware overclocker’s second worst nightmare, because of the problems it can cause. Luckily for all of us, this superb little program exists. It’s idiot-proof, really small, and fantastically effective at sleuthing out any memory instability. Because memtest86/memtest86+ tests as much of your RAM as is possible, it’s a stand-alone program, meaning it needs to be run outside of your OS.

Please keep in mind that memtest86 can still error even with a completely stable memory system/subsystem. An unstable processor, or other system problems can also cause erroring in memtest86 - your memory is not the sole potential cause of memtest86 testing errors.

"There are many good approaches for testing memory. However, many tests simply throw some patterns at memory without much thought or knowledge of the memory architecture or how errors can best be detected. This
works fine for hard memory failures but does little to find intermittent errors. The BIOS based memory tests are useless for finding intermittent
memory errors." from memtest86's Readme

There are two "versions" of memtest86 out there: memtest86+, and memtest86. Both have been updated and improved on fairly recently, and both appear to be "living" programs that are still seeing fairly regular update and improvement by their respective desigers.

The choice is really up to personal preference. Personally I've been using memtest86 for fairly long time now, and I'm very well pleased with it, but both of them are awesome softwares (so doesn’t really matter which one you choose).

You can download memtest86 here: link.

You can download memtest86+ here: link.

HOW TO USE MEMTEST86 or MEMTEST86+ EFFECTIVELY

It’s fantastically easy.

"[...]
memtest86 is a stand alone program that cannot be executed under windows and must
be loaded from a floppy disk.

To install Memtest86:
- Extract the files from the zip archive
- Open the directory where the files were extracted and click on "install.bat".
- The install program will prompt you for the floppy drive and also prompt you to
insert a blank floppy.
- To run Memtest86 leave the floppy in the drive and reboot.

NOTE: After the boot floppy has been created you will not be able to read the floppy
from windows. This is normal.
[...]" from memtest86's Readme

Note that memtest86+ can be run from a CD as well, via a pre-made, bootable, ISO image that you can download from the memtest86+ website, and then burn onto a blank CD. memtest86+ can still be installed on a floppy if one so desires, exactly as above.

After installing memtest86/memtest86+ onto a floppy, simply reboot your computer with the floppy still in the drive. memtest86 consists of 11 different tests (Note: The newest version of memtest contains only 9 tests, with the additional tests having been removed). By default, tests #1 through #7 will run in order, endlessly. For our purposes, this is perfect. Once memtest86/memtest86+ starts running, simply leave it, and let it go for 24 hours.

As with Prime95, 24 hours really is required for a complete and thorough memtest86/memtest86+ stability test, and for the exact same reasons. I’ll quote again Prime95's help file for reference sake.

"When you are stability testing with Prime95, you want to run the Torture Test for at least 24 hours. Why 24 hours?

There is a very common misconception that if your machine can pass Prime95 stability testing for, say, four hours, your machine will be able to run stable, regardless of what you are doing, for four hours as well, without issue. This is simply not the case.

Prime95 often finds errors in its 16th - 20th hour of testing, a potential for instability that wasn’t found after only four hours of testing. After only four hours of Prime95, the potential for instability still exists. 24 hours of Prime95 is a slight ‘overkill’, but you can never be too careful. 24 hours is widely viewed as a sufficient time period to catch any instability that may be present, but by all means test longer if you are able." from Prime95's Help File 'stress.txt'

As with Prime95, it’s easiest for most of us to run memtest86/memtest86+ overnight, and then the following day, so that it’s as un-disruptive as possible.

Many people also use specific memtest86/memtest86+ tests by themselves, to test out a new FSB or memory overclock quickly in order to see whether it’s likely to be stable or not. Tests 5 and 6 in particular are very good for this. However, 24 hours of all the tests on loop is your end-all solution to memory stability testing.

CONCLUSION

I really, really hope that this little guide has been helpful.

If you’ve read through the entire thing, and found it educational, then it has succeeded. If you read only the beginning, and learned a little bit about the dangers of instability, then it has succeeded.

The big goal here is for everyone to be aware of the potential for stability problems, and know how to test for them properly. This is an unrealistic goal, but every person who learns something about stability, and proper, thorough, stress testing, is one less potential victim of stability-related disaster.

I’m thinking about adding a little bit of information on the philosophies of stability, the different schools of thought on the issue, and different courses of action people take. I’m also thinking of making a little list of some of the ‘lesser’ stress testing programs, and where to get them – Some of them are very worthwhile, if inferior substitutes to the ‘Big Three’. I’ve left out really specific stress testing, such as that designed to stress test your hard-drive. The ‘Big Three’ do quite a thorough job of testing an entire system if used properly, and together, and I don’t find it pertinent to clutter an extremely long, but basically simple guide like this with arguably unnecessary information.

One thing this guide is completely devoid of is solutions to instability. This is intentional, as lots of material exists that will aid anyone running an unstable machine in getting it up to par.

If I have missed anything important, worded something really poorly, or not gone as in-depth as I should have on some issue, please PM me.

If anyone has any questions or comments please do take the time drop me a PM.

Sources, references used:

reference #1 - excellent guide written by 'felinusz' @ ocforums.net

reference #2 - awesome article @ radified.com

reference #3 - nice posts @ forums.amd.com

reference #4 - OCAU.Wikipedia about stability @ overclockers.com.au/wiki

... reserved for possible future updates ...