Overclocking Basics, What you should know before OCing Rating Options

[Verran]

We get a lot of questions around here that basically boil down to "How do I overclock?" As I've said before, this isn't a bad thing. Everyone starts somewhere and asking questions is a good way to learn, but a lot of times the answers to people's OC questions require that they know some things that they may not. I've put together some "basics" that I think people should have a solid understanding of before overclocking, and specifically before asking for help. Asking a question won't get you anywhere if you don't understand the answer, and for that reason I think this might help some people around here.

And for the record, I don't consider myself "the authority" on overclocking around here. In fact, I don't consider myself anywhere close. But I think we need something like this and I want to do my part. So to that end, if there's anything you'd like to add, please let me know. If there's anything that's wrong or misleading, I ask the same. And if there's anything that doesn't make sense to you and you would like explained better, please PM me or post here. I hope we can get this pinned so it's easier to find for everyone. So without any further delay....


OCC Overclocking Basics:


What is Overclocking?
Most people know that overclocking means to run a particular piece of computer equipment at a higher speed than it was intended to run at. But how and why is that possible?

Let's say that you have a 2.0ghz processor and you overclock it to 2.5ghz. Why didn't the maker sell it as a 2.5ghz chip? Wouldn't they make more money? The answer is that they have to sell the chips at the lowest common speed for the whole set. Every chip that's sold as a particular speed needs to be able to run at that speed on the lowest quality equipment. The makers can't guarantee what quality components the chip will run with, and therefore they have to make sure it will run with anything. This is where overclocking comes in. An overclocker will use the quality "headroom" to run the chip faster than it's intended to run. And with quality componets, this is not only possible, but also can be very rewarding.


Processor Terminology:
When someone describes the speed of their processor, they will generally use two terms: FSB/HTT and Multiplier. So what do these mean?

FSB/HTT:
FSB stands for Front Side Bus, and refers to the speed at which your processor can talk to your memory. In the AMD world, this is also referred to as HTT, which stands for Hyper-Transport Technology. This is the easiest and most common speed to adjust for overclocking. This speed setting is limited only by the motherboard, which will have a maximum selection. However, any decent overclocking motherboard should allow you to set this speed much higher than will ever be practical. If there were a single "one stop shop" for overclocking settings, this would probably be it.

FSB can be tricky with DDR memory though. DDR stands for Double Data Rate because the data uses both rising and falling edges of the clock pulses, but that's another lesson entirely. The important word is "double". DDR 400 memory actually runs at a FSB of 200 in the motherboard settings, but because it's -double- data rate, it is actually rated at 400. This very same memory can also be rated as PC3200. That means that the memory will move 3.2gb of data per second at stock speeds. The 400 and the 3200 are pretty meaningless when dealing with overclocking, however. The important part is that it will run at a FSB/HTT of 200.

Multiplier:
So now we understand the speed at which the processor talks to the memory, but how fast does it do its internal calculations? How fast does it run all by itself? The multiplier tells us this. If the front side bus is 200 and the multiplier is 10x, then we know that the processor runs at 200 x 10 = 2000mhz or 2ghz. The multiplier is a way of describing the internal speed in relation to the FSB. So taking the multiplier and multiplying it by the FSB speed will give you the actual speed of the processor.

The multiplier setting is used to overclock the chip, but not nearly as frequently as the FSB setting. The reason for this is that most newer chips have what is referred to as a "locked multiplier", which means that it cannot be set to other settings. Sometimes, this means that the setting cannot be changed at all, but more often it means that it can be set lower than stock, but not higher. Typically, if the multiplier is 10x (for example), then it can be set to 9x or 8x, but not 11x or 12x.

Voltages:
In almost every case, a chip will need more voltage than it gets at stock in order to reach is maximum overclock. But what are the different voltage settings and what do they mean? The two most common voltages that you will deal with are vCore and vDimm.

vCore is the voltage of the processor itself. This is the voltage you will use to control the chip. As overclocks become unstable, you can use this setting to increase the processor voltage and make the chip more stable.

vDimm is the voltage of the memory. This is not used quite as often, but is still important to understand. The memory can (and usually will) be overclocked as well, and vDimm can be used to increase stability in ram just as vCore can be used for processors.


Limiting Factors:
OK, so let's be honest. That 2.0ghz chip of yours just isn't going to reach 5.0ghz. We know it. But why? What are the factors that will hold a chip back? There are three main factors that will limit maximum speed of your chip. The most obvious of these is what most people call the "ceiling". No matter how good the chip is, at some point it will simply reach the fastest speed that it's capable of. The other two factors are more in depth, however.

Heat:
Heat is usually the biggest factor in a chip's performance. Higher speeds and more voltage makes more heat in the chip. And more heat in the chip can lead to failures or instability and can even lead to permanant damage if not fixed early. This is why adaquite cooling is a MUST for overclocking. This is also why it is important to monitor your system, but more on that later. Sometimes, you could know that your chip is capable of faster speeds, but it will run too hot and therefore will be limited in its speed.

Voltage:
Increasing voltage can make an unstable processor stable, but it's more complex than that. Processors are not meant to run higher voltages than stock, and can be damaged by too much voltage even if heat is managed properly. Just like with heat, a processor could reach a point where it can go higher but it might be at a voltage that isn't safe and therefore isn't recommended.


Dividers:
In my opinion, memory dividers are under-rated in the overclocking world. A lot of times, an overclocked system will reach an instability or fail point, and it will not be clear whether the processor or the memory has failed. For this reason, people are always looking to test one part individually. A memory divider can let you do this.

Memory dividers allow you to run the memory at a slower speed than the chip. So, for example, you could run your chip's FSB at 250mhz, but run the memory at 208mhz. This is done using a 5:6 memory divider. (250 * 5/6 = 208) By doing this, you can slow your memory down to stable speeds and only overclock the processor. This allows you to attribute any instability directly to the processor, rather than having to guess what is causing it.

Slower memory speeds are often undesirable for a system, since they slow the memory down, but they can be used for two reasons. First is for testing, as mentioned above. By slowing the memory down to stock speeds or lower, you can be sure that the memory is not causing overclocking failures. The other reason to do this is that some processors simply can't support memory speeds that high. By slowing the memory down, some chips can actually overclock much further, so even though the memory is slower, the system as a whole will run faster.

Memory dividers can also be referred to as "max memory speeds". A 5:6 memory divider may be referred to as 166 max memory speed, since 5/6 * 200 = 166. Another example would be a 1:2 divider and a 100 max memory.


Monitoring:
As mentioned previously, it is highly recommended that an overclocked system be monitored in many ways. Many software packages monitor things like temperatures, voltages, fan speeds, clock speeds, memory settings, etc. Monitoring these readouts allows you to find and solve problems before they become serious. If you don't watch these readouts, you may not discover a problem until it is too late and damage has been done. Here is a list of some of the most popular programs:

CPU-Z (link)
This program is probably the most widely accepted speed monitor out there. It can tell you all the pertinant information about your processor, including speeds, FSB, Multiplier, voltages, memory speeds, memory settings, and much more. This is basically a "must have" program for overclocking.

CoreTemp (link)
A newer temperature monitoring program to support C2D and newer dual and quad core processors. This is a current standard and can measure individual temperatures for each core on multi-core processors.

RealTemp (link)
This is very similar to CoreTemp but generally reports lower temperatures due to an adjusted "TJ Max" value in the calculations. This is also handy because apart from reporting current temperatures, it also reports minimum and maximum values over the duration that the program is left running.

Motherboard Monitor (link)
This is a widely used program which is generally targetted at monitoring temperatures, but can also be configured to show things like voltages and fan speeds. By default, the program will display the case and processor temperatures in your system tray. The program is somewhat "out of date" and doesn't support many new motherboards without modification, but is still widely accepted as a standard.

ITE Smart Guardian
This program has different versions for different motherboards, so make sure you download the appropriate one. For this reason, there is no link. The program monitors temperatures, fan speeds, and voltages. It is regularly used on newer motherboards in place of MBM5.

SpeedFan (link)
This is very similar to ITE Smart Guardian in that it monitors temperatures, fan speeds, and voltages, but it can also be used to change fan speeds at the software level.

Everest (link)
This program can be used to access temperature, fan, and voltage info much like the others listed above, but its real value is in the ability to get TONS of useful information about your computer. It can tell you pretty much anything you want to know about your PC, statistically speaking. I have found this program useful for varifying the BIOS version of my motherboard, though there are MANY other uses for it.


Stability Testing:
Overclocking is fun and beneficial, but can also cause major problems with your PC. A computer that is improperly overclocked can cause crashes, reboots, power-downs, data corruption, and eventually even permanant hardware damage. Again, it is important to diagnose these failures early on so that they don't escalate to bigger problems. This is why ANY good overclocker will have a toolbelt full of stress/stability tests to check their system with. An overclocked PC does you no good if it's not stable. Running games faster does you no good if they crash at random. Overclocking needs to be kept in check with stability testing whenever settings are changed. Different people will have different definitions of "true stability", but all overclockers should know how to test for it. Here is a list of commonly used stress test programs:

Prime95 (link)
This is a distributed computing project, but can also be used strictly for stability testing. As with most programs, it uses strenuous math calculations to see if your processor ever produces failures (wrong answers). If there were a single universal "final stability test", Prime 95 could arguably take that title. It is widely accepted and very reliable.

OCCT (link)
This project is no longer being continued, but the tool is still incredibly useful. OCCT has two modes: A standard stability test and a torture test. The standard test runs for 30min and is a very good stability indicator. After the 30min test completes, it shows graphs of temperatures and voltages which is a feature that is not really found in other programs, and is very useful. The torture test simply runs until stopped and reports any instability, much like Prime 95.

SuperPi (link)
SuperPI is actually a benchmark program, and gets its name from the calculations of Pi digits that it performs. SuperPI speeds are a good indicator of a processor's speed, but the tests will also report instabilities as they occur. This program can run very quick stability tests that are surprisingly accurate given their speed. This is another "must have" in my opinion.

MemTest86 (link)
This test is used to test just your memory, as the name implies. It can either be booted from a floppy disk or a CD-ROM. Once it is booted and running, it runs multiple test patterns on your memory until it is stopped, and reports errors as they happen. This test is very good for testing the memory alone, and helps to confirm that your memory will run at the speed and voltage you have set.

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That's all for now. Hopefully this information will make the world of overclocking a bit more understandable. If this guide gets good response, I hope to continue the saga with further overclocking guides. Thanks for reading and good luck with your overclocking...

[martymcfly]

There is one BIGGIE that needs to be included. You explain what OCing is and what you need to change, how much, etc., but an important thisng to tell people is the most basic thing, where to actually do this. Maybe a mention of the BIOS would be sufficient. Also put something about not using windows software to overclock also.

[boinker]

awesome Varren. once more +1

[Bosco]

I forgot about this I think we should update this a little.

[itsmee]

Cheers Verran.
Concise yet very helpful. Much appreciated.
All you need to do now is a walkthrough for each processor and you'll be a superstar.

PS: Any chance of one for the i7 by Wednesday morning. I'll swap it for the mother-in-law?

[anep]

which one better if i using AMD to get 3000Ghz higher multiplier or frequency? 250x12 or 200x15

[Waco]

which one better if i using AMD to get 3000Ghz higher multiplier or frequency? 250x12 or 200x15

99% of the time it makes no difference either way. Personally I'd go with cranking the multiplier simply because it's so damn easy.

[anep]

but the voltage needed to be stable different..

[xlrwrite]

Wow, lots of good information there to get my feet wet! Thanks a bunch to the OP.

[Ste]

Probably should mention stuff about cooling, lapping, diff thermal pastes, different heatsinks, liquid cooling, peltiers and other solutions..

[damian]

Probably should mention stuff about cooling, lapping, diff thermal pastes, different heatsinks, liquid cooling, peltiers and other solutions..

Read the title
Overclocking Basics

This post has been edited by damian: Apr 29 2009, 06:14 PM

[Verran]

Sorry, but there's really no chance of the cooling stuff showing up here. The guide is already too long IMO and by that rationale there are way too many other topics that would need to be touched on as well (voltage, current, resistance, Ohm's law, case materials, fan sizes and speeds, motherboard layouts, hard drive types, IHS dynamics, power supplies, etc, etc). I understand the desire to inform the user on all fronts but my intent with this guide is to cover only the basic essentials that people need to understand to start overclocking and to ask informed questions about their overclocks.

EDIT###
Also, I've added some color to make navigation easier and added a few newer programs to the lists. I may go through and update more later. Most if it was written to be generic enough to still apply, but the section on memory dividers might be unnecessary now as memory multipliers have stuck around but most current boards don't seem to offer dividers anymore.