The Absolute Basics on how to Overclock your CPU

Discussion in 'Links' started by Joshua, Aug 20, 2002.

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  1. Joshua

    Joshua Ancient Guru

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    Reasons to not Overclock
    1) Protection - Warranties are voided on almost all CPUs, and some motherboards as well.
    2) Stress - More Stress on the CPU (and on all devices if you increase the FSB)
    3) Heat - More Heat Generation from CPU (and RAM if you increase the FSB)
    4) Sensitivity - The heat sensitivity of your system will be greatly effected. If you o/c in the winter and summer comes around, you might be forced to reduce your speeds because your system cannot work stably with the large change in ambient temperature.
    5) Efficiency - Increasing your CPU speed with overclocking doesn't increase it's efficiency at processing data. For example, an AMD TBird 1.0 overclocked to 1.4 will NOT be as good as an AMD XP 1.4, simply because the XP has many more optimizations, such as a full SSE instruction set to name one.
    6) Hassle? - Some people get fed up with having to constantly adjust their system for stabilty. Other, however, find this the most intriguing and education part of overclocking, so it's your call.

    Reasons to Overclock
    1) Speed - Your CPU will perform more operations per second (and your RAM if you increase the FSB)
    2) Ca$h - Who needs a to buy a "pricey" 1900+ when you can get a 1600+ for half the price and overclock it to the same speed?!
    3) Troubleshooting - an Overclocker HAS to know what is going on in their system, because if he doesn't, he'll have an unstable system. Being able to overclock successfully will educate a person on vast areas. Everything from CPU temperatures, to BIOS updates, to OS drivers, to motherboard jumpers. This knowledge is invaluable.
    4) Bragging Rights - Everyone knows that the first thing they're gonna do once they have a nice big overclock is plump it into their Guru3D signature and post a big ol' happy thread about it :)

    Safety Procedures

    KNOW WHAT YOU HAVE - If you are trying to overclock, and you come in and post a thread saying "Help me overclock", we will only be able to help you if WE KNOW what motherboard, CPU, heatsink/fan, RAM, operating system, video card, and add-on devices you have. And the only way WE can know this is, obviously, if YOU tell us. So KNOW what you have.

    UNDERSTAND WHAT YOU'RE DOING - The term "Overclocking" is actually very general. There are several ways to overclock a CPU and other components. Please read MORE than what I'm about to provide here, the intricasies of these components can span pages... While overclocking, you will change several or possibly ALL of the following:

    Front Side Bus (FSB) - This is how fast your motherboard chipset communicates with your CPU, and is also one of the two factors that determine overall CPU speed in MHz.

    CPU Clock Multiplier - This is a unitless value, who's value increases or decreases in 0.5 increments (such as 10.0, 10.5, 11.0, etc) This value only affects the CPU, and is the other determining factor in overall CPU speed in MHz, when multiplied together with the FSB.

    CPU Core Voltage (Vcore) - This is the amount of voltage your motherboard will stream to your CPU. An INCREASE in voltage will ensure that your CPU will cleanly pass data, and will prevent data corruption when your CPU is running at higher than stock speeds. An increase in Vcore will also increase your CPU's core temperature. Find out what your specific CPUs voltage is, because not all CPUs use the same voltage. Look at or

    RAM Volage (Vio) - This is the amount of voltage your motherboard will stream to your RAM modules. Similar to Vcore, it ensures stabilty at higher speeds, although you will only need to increase this value at high FSB speeds, not high Clock Mulitplier settings.

    Once again, a reminder to please go out and find more resources on all and MORE data regarding what exactly happens when you "overclock". That term is not specific in the least.

    DON'T RUSH - The best thing you can do when overclocking is to not rush. Rushing will most likely lead to failure, which leads to aggravation. And there's definately a possibilty of killing your CPU, motherboard, RAM, etc. if you rush.

    TEMPS, TEMPS, TEMPS - Any overclocker will know how well his heatsink removes heat from his CPU, and he will measure this using the temperature sensors that almost all motherboards include. Using either the BIOS or other software (such as Motherboard Monitor for Windows) will provide you with real time temperature values. Research to find out what acceptable values for your CPU temperature are. I can tell you that all AMD Athlon and Duron CPUs should ABSOLUTELY and WITHOUT QUESTION be under 70C. If you are overclocking, you will require a much lower temperature. The reference point I usually recommend to overclockers is 60C at full load. Please note, that by "full load" I am suggesting a CPU intesive test. The best one I've seen is Sandra 2002's Burn In Test. Run 50 passes of the two CPU benchmarks using Sandra's Burn In function, then check your CPU temperature. If you are under 60C, you are safe. You can find Sandra at

    CHECK EVERYTHING - My last safety suggestion would be to always take your time... make sure your heatsink is installed properly on your CPU and make sure you used a thin, even layer of thermal compound. Make sure your heatsink was perfectly clean before installation. Make sure all your fans in your case and on your heatsink work properly. Make sure your RAM and all PCI devices are snugly in your board. Make sure all cables on the back of your PC are snug.

    Following that simple guide, you should be able to cut back on the amount of problems and frustrations you have when overclocking.

    Increasing the FSB will affect the CPU and also nearly all devices in your system. This is both good and bad, because in a stable system, while all devices will benefit from a slight boost, this also means all devices are stressed more than usual.

    Increasing the CPU Clock Multiplier will only affect the CPU. What MOST overclockers do is increase the FSB and leave the clock multiplier alone. What the HARDCORE overclockers do is lower the multiplier first and then MAX OUT the FSB.

    There is no reason you should ever LOWER the FSB from stock speeds, unless you're in an emergency of some kind. It will NOT help in overclocking
    Last edited: Aug 20, 2002
  2. Psychosematic

    Psychosematic Ancient Guru

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    Overclocking Guide - Part II

    A closer look at overclocking, by Psychosematic

    I came across my old introduction to overclocking posts (above) and now that I look back, I feel compelled to expand upon the topics mentioned, and delve into deeper thought.

    Overclocking today could be considered very common. PC retailers are beginning to give you the means to overclock your computer very easily, and some are even doing it for you. Now that overclocking is everywhere I look, I'm attempting to take it a step further and become a master overclocker. So, here's what I've learned along the way...

    Same product does not mean same results!
    A lot of newcomers will search around and come across overclocks that really catch their eye... "AMD Athlon XP 1700+ at 3000+" and so on... Typically, someone will want to know exactly what hardware was used, in an effort to duplicate either part, or all of that person's overclock. Well before you get all excited, realize some important facts.

    1.) PC hardware can yield the same name, but in fact be different in important ways. For example, most of you know, Athlon XPs come in several flavors... Palomino, ThoroughBred, ThoroughBred B, and Barton. But it goes even farther than that. CPUs of the same name and core have "revisions" during their manufacturing process, commonly called "steps". Each of these steps usually has a character code like "AGOGA" or "AXQCA". Depending on which "stepping" CPU you have, your overclocking results will vary. When researching an overclock someone has done, try to find out what core and stepping version they have, if you wish to duplicate it. In summary, there is a big big difference between an Athlon XP 1700+ Palomino AYHJA Stepping and an Athlon XP 1700+ ThoroughBred B JIUHB Stepping, so please realize that there's more to it than Athlon XP 1700+

    2.) Motherboards can have similar characteristics... depending upon when you get a specific model of a motherboard, it may or may not have a revision to it's chipset. In addition, newer shipments of the same board typically come with newer BIOSes flashed to them. The model number can tell you a lot, but it can't tell you everything. Your best bet is to look at the POST screen when you boot and write down the BIOS version number, and any board revision numbers you see. You may even want to inspect the board itself for model numbers both on the PCB and on the north- and south-bridges.

    3.) Upgradable Firmware is installed on different hardware devices, most commonly CD-RW and DVD drives. You can think of firmware as a BIOS for an optical drive. It's best to upgrade from the manufacturor's website periodically, and be sure to follow their instructions. Flashing firmware is short and sweet, but can cause a load of problems if you use the wrong firmware or have a system crash during a flash. For this reason, always flash on a system that's not overclocked (or at least not SEVERELY overclocked) with no other programs running. New firmware can make a world of a difference in stability and performance.

    4.) Software plays a big role in overclocking results... proper drivers are, of course, required for best performance. Keep a close eye on your motherboard manufacturor's website for driver updates, and you may want to periodically inspect for OS updates that can help stabilize your system. Above all, please make as few software changes at one time as possible. This means registry tweaks, driver installations, software installations, etc. THe more you do at one time, the less an idea you have of what is causing the problem. Always take notes during the setup process, so you know exactly what works and exactly what doesn't work.

    Have you got the power?
    The Power Supply Unit is always one of my first topics... it's one of those things that are essential, but so very easy to neglect. And when you spend days hunting for the hinderance to your overclock, it all could begin with a weak or faulty power supply. There is absolutely no reason to skimp when it comes to which unit you choose for your system. PC retailers (online especially) are selling some pretty decent looking cases for short money, and they even include a "550w AMD APPROVED POWER SUPPLY!" Well my advice here is BE CAUTIOUS! If it's too good to be true, it probably is. Consider the street price of a top quality 550w power supply... $100 or more. If someone is selling an $80 or $90 case to you with a 550w power supply in it, it's probably not even worth turning on. If you're curious as to how these power supplies could be as bad as I say they are, here's my explanation. Power Supply companies send their units to AMD for testing. If AMD can run their test system without any problems, it is approved. This is all well and good, but there are TWO IMPORTANT FACTORS that are simply not tested. One is the wattage rating... They can slap whatever sticker they want on it after it comes back from the AMD labs. 550w? SURE! Not to say they are false advertising, but 550w is a MAXIMUM under VERY UNLIKELY circumstances, i.e. 50°F ambient air temperature and 100% pure power coming through the line. The next untested factor is it's ability to withstand an overclock. Overclocking often required overVOLTING, which adds stress to the power supply. Generic power supplies often can't provide 100% clean voltage to begin with, so why trust them to overvolt for you? To sum it up, be aware that a wattage rating can be a ploy to get you to buy, and overclockers should be aware of these cheap ploys, and buy with confidence. Your PSU runs your entire system, and you should not have any doubt as to the quality and quantity of power it is using. I suggest Enermax, Antec, and PC Power and Cooling as the best in power supply units. It's hard to recommend a minium wattage rating, because every system is different. But I can tell you that anything below 350w on a quality power supply will be a hinderance to your overclock.

    How far is too far?
    We've all heard of hardware labs running extremely overclocked systems, cooled by such contraptions as a dry ice case or liquid nitrogen. While it's entertaining to read that a Pentium 4 2.8GHz can break 4GHz, it's not realistic in terms of daily computing. It's reasonable to assume that us overclockers will spend a good amount of time on our systems. Or at least, the systems will be running for quite a bit of time. If that's the case, there are certain restrictions you should put when you attempt to overclock.

    1.) CPU voltage (vCore) is a very important variable in overclocking. Stock voltages today roam around the 1.65-1.75v area. Some motherboards, however, are capable of pumping upwards of 2.0v to the CPU, and people have even physically modified their boards to increase the CPU voltage even further. Well, my friends, the impact here is quite simple to understand. Even when properly cooled, a 1.65v CPU running at anything higher than 2.00v is downright dangerous. Not only will this put a significant stress on your power supply, but the CPU itself is under extreme duress. While your system may work and work flawlessly, you can't expect it to run for months and months or years and years without a problem. Personally, I restrict myself to 1.85v when increasinve the vCore on my 1.65v CPU. With extreme cooling, it would probably be safe to go to 1.90v or even 1.95v. But I will continue to discourage such extreme overvolting, unless you are prepared to spend as much money and time as possible on getting an EXTREME overclock.

    2.) RAM and RAM voltage (vIO) are also important. RAM sticks themselves come in all shapes and sizes. Anywhere from 64MB to 1GB sticks of DDR can be purchased, and these come in speeds from PC1600 to PC3700 and probably faster. Yet again, these sticks are rated for specific latencies. You must be award of what speed and latency your RAM is capable of when overclocking! DDR RAM (sorry for the RD people, I'm simply not up to snuff on my RD statistics) typically runs at 2.5v. For overclocking, this may need to be increased to insure the memory will cleanly pass the data. If this is the case, I put the following restrictions on myself when increasing RAM voltage: For bare RAM without heatsinks, 2.7v. For RAM with passive heatsinks/heatspreaders, 2.8v. For RAM with heatsinks/heatspreaders and active cooling, 2.9v. Again, people have modified their motherboards to provide upwards of 3.0v to the RAM, and I simply cannot condone it unless you have the money to back up your risk. Also be aware, if your PC is in a hot place and/or you have little (less than 3) case fans providing airflow inside the case, it is wise to keep severe restrictions on your vIO. Latencies are typically safe to lower, but they WILL cause your PC to crash when set too low, and that leaves the possibility of data corruption. When overclocking the memory by ANY means (overvolting, increase FSB, and/or lowering latencies) make SURE you don't have any essential data connected to your system via hard disk drives or otherwise. And once again, only ONE change at a time, so you know EXACTLY what causes the problem.

    3.) PCI and AGP voltages above stock levels can adversly affect both performance and the life of your hardware. Personally, I always leave these voltages at stock levels, but many people feel compelled to push everything that can be pushed! If that's the case, always test ONE component at a time, including the video card in your AGP slot. This way, you can see which piece of hardware has the limitation; you can limit stress on the motherboard and power supply; and if a voltage is consequently too high, there are minimal risks of damaging your components, since there is only one removable component in the system.
    Last edited by a moderator: Jan 17, 2005
  3. Psychosematic

    Psychosematic Ancient Guru

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    Conclusions and Final Words
    If there's anything you get out of this little blurb, just know that patience is the ultimate overclocking tool. Rushing can do so much more harm than good, and having the sence to do lots of research prior to overclocking, testing only one overclock at a time, and taking notes during the entire process will save you in the long run.

    If you disagree with my personal restrictions and suggestions, I welcome your constructive feedback. I'm certainly nowhere close to an overclocking expert. I learn as I go, just like everyone else.

    I hope this sheds a little more light on the overclocking scene. Now that everyone and his brother knows what overclocking IS, it's time we all educate ourselves on proper methods of overclocking, and what exactly to expect when we overclock.

    Thanks for reading!
  4. Royicus

    Royicus Ancient Guru

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    The Absolute Basics on how to Overclock your CPU

    I have been seeing many questions about people wanting to overclock their CPU's lately, so I decided that I would type up a general guide on how to do it.

    First, neither I nor anyone here will accept responsibility for damage to your computer, loss of data, loss of revenue or income, personal injury, injury to your pet, or any event resulting from following this guide. You follow this guide and overclock at your own risk.

    Since you are still reading, I assume you accept the risks.

    Getting into your BIOS
    1) You need to get inside your motherboard's BIOS. This is usually done by hitting the "delete" key when your computer is POSTing, which is what your computer first does when you hit the power button. If you are not sure, just keep hitting the button when you first turn on your computer. Some motherboards or computers do not use the "delete" key to get into their BIOS. To find out your key, just look at your motherboard manual or look it up online.

    Important Stuff in the BIOS
    2) Now that you are inside your BIOS, there are some things that you need to hunt for:

    - CPU Clock ratio/Multiplier: This is going to be a number from around 10 up through 20 or so. You can find what your multiplier is by looking up your processor online. For instance, an Athlon XP Barton 2500+ runs at 1.83 GHz on a 333FSB. Since that FSB is twice the actual value, you take 333/2 = 166. Take your operating speed, in this case, 1830MHz, and divide that by 166MHz, which results in 11. Therefore, the multiplier for an Athlon XP Barton 2500+ is 11, its total operating speed is 11x166MHz = 1.83GHz. Pentium 4's use a FSB that is 4x the actual value. So a P4 2.53 on a 533 FSB is (533MHz/4)*19 = 2.53GHz. You can see from this calculation that the multiplier for this processor is 19.

    - FSB Frequency/External Clock: Again, this could be under a different name, but this will be the default setting you’re your CPU's FSB. Depending on your processor, this will be either 100, 133, 166, or 200 MHz. This setting is the bread and butter of overclocking. Increasing this number is what results in your largest performance gain.

    - CPU FSB/DRAM Ratio/Memory Frequency: Again, this could be under a different name. This setting allows you to chance the ratio between your FSB and the frequency of your RAM. Since you are reading this, I assume you are new to overclocking, and I would recommend you set this to a setting that is 1/1 equivalent. So yes, that could be 2/2 or 3/3 or 6/6. Anything that reduces to 1 is fine.

    - CPU Voltage/CPU Core Voltage: This number is going to have to go up if you do any real overclocking. When you increase the operating speed of your processor, you need more voltage to keep it running stable. If you do not increase this appropriately, your computer will crash, and you could potentially lose or corrupt data.

    - DDR SDRAM Voltage/DIMM Voltage Regulator: Again, could be under a different name. Like your processor, increasing the speed of your RAM will sometimes make it unstable. Increasing the voltage, just like with your CPU, will sometimes make this run more stable.

    These are the basic settings that you need to change get started in your overclocking endeavor. However, you still need some programs that will ensure that your computer is running stable, and you won't corrupt or lose data. For this you will need a program that can test the stability of your computer. I recommend Prime95 (to check your CPU) and memtest86 (to check your RAM). Both of these programs are free to download online. Read their instructions for information on how to use them, but basically you want to go under "options" and run the "torture test" for Prime95, and just let memtest do its own thing. Both of these programs will alert you to an error. If you do get an error, that means you need to back off your overclock, or increase voltage to whatever component is faulting.

    Word of Caution about Voltage
    Now as a word of caution, since you are new, I would recommend that you not increase voltages by more than 5% of their stock values, especially if you are running on standard cooling, or the heatsink and fan that came with your processor. If you are running a high performance heatsink, then you can be a little more liberal (about 10%), but keep an eye on your temperatures. Your temperatures can usually be read using motherboard monitoring software that came with your motherboard, or you can download some software online. Just make sure that it works with your particular motherboard.

    Starting to Overclock
    Now, to begin overclocking. Go into your BIOS and increase your FSB Frequency by about 5 - 10 MHz or so. Boot into Windows and run Prime 95 for maybe half an hour. Keep an eye on your system's temperatures. Generally, you should keep your CPU load temperature (the temperature when running Prime 95) under 55 or 60 C. If it successfully completes a half hour, and your temperature is low enough, then go back into your BIOS and up it by another 5 or so. Repeat until Prime 95 returns and error, or your computer is running too hot.

    If you computer ever runs too hot, stop overclocking, back off a bit on your FSB and voltage, and leave it there (make sure that it is stable using prime 95 and memtest) Make sure you do not run 65+C, or you run the risk of damaging something. Keeping it under 60C at full load is always good practice. In addition, I recommend that you get a good heatsink and fan before you even start to overclock. Keeping your CPU at acceptable temperatures is very important.

    Your First Error
    Once you get that dreaded error (and yes, your heart may sink, that's ok), you need to increase voltage. Go by the smallest increment possible and run Prime 95 again. If you are able to pass this time, continue upping the FSB and voltage until you reach a 5% or so increase in voltage. If you cannot pass, then increase the voltage a little more (one more increment) and try again. Like I stated before, only increase your voltage by about 5%. Once you hit that voltage, stop. When you think you have found your best overclock, run Prime 95 for several hours (preferably overnight or for a day) to make sure that your computer is stable. If it returns an error, then you should back off your FSB by about 5MHz or so and try again. This process is very time consuming, but you want to ensure you are running a stable computer.

    Are You Done?
    Now what? Have you hit your maximum overclock? The answer is most likely, no. There are several little tweaks you can use to increase your overall clock speed. First, find out what is limiting your overclock. This can often be the CPU, motherboard, or RAM. To find out if it is your RAM, run memtest. If that returns no errors, then it is likely the CPU. If memtest does return errors, then it is likely either the motherboard or RAM. Try to increase the RAM voltage and see if you can get memtest to return no errors. If this does not help, then it could still be the RAM or motherboard. Sometimes, if your power supply is weak, that can actually limit your overclock. Your voltages should be within 5% of their nominal value. If you are overclocking, I would recommend a 400+ watt power supply from Antec, Enermax, or OCZ, but there are many brands out there and many threads here at guru on this topic, so search for one of those threads and see if you can't find a power supply well suited or you. Generally, I would look for 25A+ on the 12V line (that's 25 or more amps on the 12 volt line).

    Are You Done Yet?
    Still aren't running stable? Try reducing your multiplier. Increasing your FSB is the most important factor in gaining real world performance. So, reducing the multiplier and increasing the FSB is a great way to get more performance. However, your motherboard or RAM will limit you here. For instance, you can run 10x220 to get 2.2GHz or 11x200 to get that. The 10x220 will run faster than 11x200 even though the processors run at the same frequency. Keep in mind here that your RAM or motherboard will be the limiting factor here, as long as you know that your CPU can run at whatever frequency you are running. Take for instance the 11x200. I know my computer can run that, but if it can't run 10x220, I know either my RAM or my motherboard is holding me back. Try increasing your RAM voltage by few notches to see if you can achieve a stable overclock.

    So, you've increased your RAM voltage and still can't get it running stable. Now is it game over? No, not quite. You can try and loosen up your memory timings. You will see these values as something like 2-2-2-5 or 2-3-3-6 or 2.5-3-3-7 or 3-4-4-8, or something similar to that in your BIOS. Generally, I would leave these alone because increasing your timings can actually result in worse performance, even though you may be able to increase your FSB. As an example with my computer, running 200 MHz at 2-3-3-7 gave me 1423MB/s of throughput. Running 2.5-3-3-7 at 213 gave me 1486MB/s. As you can see, for 13 more MHz, I gained almost nothing (and you certainly won't notice a performance gain from that). Running 2-3-3-11 at 200MHz gave me 1373MB/s. Finally, running 2.5-3-3-7 at 200MHz gives me 1398MB/s of throughput. So keep in mind that relaxing memory timings is not always the best idea. This option is more geared towards advanced and seasoned overclockers, so just leave this alone for now until you get more experience. The only reason I am sharing this is just to let you know it exists.

    Ways to Spend Money to Get More Clocks
    Now that you have overclocked, you are wondering if you can push it farther, yes? Well, the answer is, of course! However, that may require some money. Purchasing components that are known to overclock well is always helpful. So buying new RAM, a motherboard, or processor that is known to be able to achieve high speeds will likely allow you to overclock farther. Also, if you were limited by temperature (reaching 55 - 60C or so), you can invest in a new high performance heatsink or water cooling. This will cool your processor down more so you can increase your voltage. Also, something that is equally as important as your heatsink and fan is your case cooling. If you can, get more case fans to lower the temperature inside your case. This will result in your processor running cooler. This is very important. Like I said, the things mentioned in this paragraph will require you to spend money. If you are not that serious, then I would recommend you don't really buy anything. However, if you enjoy this, and you want to get into it more, then by all means, help boost the global economy and buy more stuff.

    This guide is just intended to introduce you to overclocking, and help you gain your first extra clock cycle. While you spend time with your computer, you will get to know how it performs, what it can do, and what it can't do. For instance, I know that I cannot run more than 213 FSB, and that my Athlon XP-M 2600+ will do 2.55GHz at 1.75V. I also know that I can run 2.6GHz at 1.85V, but that generates too much heat to keep a quiet system. Over time, you too will start to gain intimate knowledge of your computers inner secrets. So, go on into your BIOS and see if you can't increase the power consumption and speed of your computer!! Enjoy!


    BTW, please remember that we can never tell you exactly how much a certain component will overclock because every component is different, even if it is from the same batch you will see different results. So please, bear this in mind. If you need to find out how far something overclocks in general, look around at people's specs and see how they're doing, and if you end up having to ask, please be as specific as possible.
    Last edited by a moderator: Feb 5, 2005

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