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CPU Guide

From OCAU Wiki

This guide was meant to be read the whole way through, it is titled for convenience when going back over things, I strongly recommend reading the entire guide before resorting to creating a new thread and asking something that could have been answered here..

If your new, and are having trouble understanding what I’m talking about, I recommend that you keep reading, and through example or just more knowledge you will understand, if however this ISN'T the case and the article ISN'T informative enough or it has some incorrect information, email Spamzor at:

This guide is Copyrighted by Spamz0r 2003-2004 (excluding ALL material used, if i have used something that isn’t referenced please contact me at the above address)

NOTE: This guide was originally created by Spamz0r here for the OCAU forums. It is replicated here with a bit of formatting - z3099528



Overclocking can KILL system components if taken to the extreme or not carefully, it’s important that in doing this, it is at your own risk, and you will void your overclocked parts warranties, I cannot be held responsible.


Order in performance of cooling methods:

  1. Liquid nitrogen (Ln2 or N2(l))
  2. Phase change
  3. Peltier/water cooling
  4. Water cooling
  5. Standard heatsink with fan
  6. Passive (heatsink no fan)

Liquid Nitrogen

Price: 2L about $2 AUS

Liquid Nitrogen relies on the process of phase change, when a liquid boils it 'absorbs' surrounding heat. Because Liquid Nitrogens boiling point is -195.798ºC it cools extremely quickly when placed out side its canister. It is stored at room temp, but it cannot evaporate when sealed. (equilibriums are reached within the canister)

Liquid Nitrogen is not a permanent solution. It generally is used for a brief period of time when a (some what professional) overclocker wants to push his/her machine to absolute extreme. Hardware can often die when the hardware expands back to its normal size.

It is normally either placed inside a small copper cup which is placed on the CPU core, or put directly onto the core

Temperatures can get close to -195.798ºC

Phase change

Price: (pre-built) $600 - $1500

A very good cooling method offering below 0ºC temperatures.

There are currently a few pre-built solutions available such as [Vapochill] and [Prometeia]

To talk to people that own these cases or have built there own DIY phase change rigs, Check out these forums:

Temps can get below -30ºC (with the right gas and setup you can get to -150ºC)

Peltier / water cooling

Price: (cost of water cooling not included) ~$20 - ~$80

A TE peltier (to put it very simply) uses a lot of power to reverse conditions on either side, so one side gets extremely hot, while the other gets extremely cold, the water cooling is used to cool the hot side (see #3 about water cooling)

This can offer below 0ºC temps, however this is not as effective as phase change, and an additional PSU might be required to power the peltier.

Temps can get below 0ºC

Water cooling

Price: $30-$200 for pump, $15-$150 for waterblock, $20-$200 for radiator, $40 for tubing and misc (pre-built can range from $150 - $500)

Using a "waterblock" which is a Copper or Aluminium (sometimes even silver) block, with usually one in and one out barb (direction usually does not matter) hosing is used to connect the water block to a pump, and a radiator this is an inline system, you can also include a reservoir, but this merely delays the time it takes the water to heat up

This can be very effective but costly as well.

Temperatures can get a 0-20ºC degrees above ambient

Standard heatsink with fan

Price: $10 - $150 not Inc fan

Blocks of thermally conductive metal (and thermally capacitive metal) machined to have maximum surface area, while being light, and small, the more surface area allows more heat to leave the metal and be transferred to air which is being moved very quickly by a fan. For example, thermal capacities of 5 (silver has been used in a HSF before!)

Common HSF elements

Note that heat capacity is how much energy (J) a solid can store at a given temperature. As the heatsink goes to thermal equilibrium, this value has a diminishing effect on heat transfer.

  • Aluminium

Heat Capacity 897 J/kg-K Thermal Conductivity 237 W/m-K

  • Copper

Heat Capacity 385 J/kg-K Thermal Conductivity 401 W/m-K

  • Oxygen (air will be different though, but not by a large amount)

Heat Capacity (O2) 918 J/kg-K Thermal Conductivity .0024 W/m-k

  • Water

Heat Capacity 4178 J/kg-K and Thermal Conductivity .320 W/m-K

  • Silver

Heat Capacity 235 J/kg-K Thermal Conductivity 429 W/m-K

(Thanks goes out to Mattmedia for these conductivity ratings!)

So a faster fan can lower temps, but a fast fan can't make all heatsinks perform better.

A few more basic rules apply to metal heatsinks (this includes all metals that come in contact with your CPU core) and contact with your CPU. The base of the heatsink must be EXTREMELY flat, to ensure very good and even transfer between the CPU and the heatsink. However the smoothness does not need to be applied to the entire heatsink, only the base. The purpose of a thermally conductive medium in between is to fill all the microscopic gaps in the metal and core of the CPU as air is very bad in comparison to micronized silver etc

If you want to compare a HSF go here It has every single Heat-Sink imaginable all benchmarked and tested.

Temperatures get a fair bit higher than ambient (0* - 60ºC + above ambient).

(It is possible, If I run a Celeron 600 de-volted with an slk-800 the temps are just about constant at ambient)

Passive (heatsink no fan)

Same basics as above, normally passive heatsinks are only used on smaller applications such as northbridge chipsets (not CPUs) for a number of reasons:

  • Cheaper
  • Quieter
  • Smaller

While there aren’t any standard (stock) heatsinks that can cool today’s latest Intel and AMD generation of CPUs, aftermarket solutions are available, such as the Scythe Ninja, which can cool most modern processors effectively without a fan on the heatsink itself. These tend to have much more widely spaced fins, and be much larger, than standard heatsinks.

Passive solutions require careful management of case airflow and do not negate the need for at least some forced airflow to be present.

The only readily-available CPUs sometimes shipped with a passive heatsink as stock are the lower-speed VIA C3 mITX CPU/boards, intentionally designed to run passively. Price: $10 - $150

Overclocking 101

Overclocking is a modern day art in which a CPU can be run at a faster speed/clock than its default Anything can really be overclocked. yes even a clock (no not really – that’s so lame)

But when it comes to overclocking there are some sane limits of what can and cant be overclocked here is a list of what is possible:

  • RAM - Yes, you can overclock this, by increasing your RAMS FSB or by lowering your latencies lower than stock.
  • Video Card - Yes, you can overclock this, however at the moment the only way is through an operating system, instead of the bios (which is better!)
  • Sound Card - Soundcards are in theory overclockable, but as the PCB and designs of the controller doesn’t allow adjustments the only other way you would possibly make it run faster is by taking up the PCI bus - not recommended.
  • Modem - No. There is some tweaking you can do, but if your on 56k... sorry pall your most likely screwed
  • Hard Drive - HDD's are "overclockable" in such that you could replace the HDD rotary motor.... although that in itself is incredibly hard.
  • Optical Drives (CDROM/CDRW/DVDROM/DVDRW) - There are quite a few drives on the market that can be flashed to a faster model, this usually results in a perfectly 'overclocked' drive!
  • [Motherboard | [Northbridge/Southbridge]] - NB can be overclocked by increasing your FSB (GENERAL rule of thumb, overclock your FSB and overclock anything attached to your NB/SB, however on newer motherboards there are locks stopping this from happening which is good!)
  • Calculators - I have overclocked my Ti83+ Texas graphics calculator, which involved increasing the voltage into the chip, I believe the core runs as fast as there is Voltage going into it, it currently is running 3 times as fast. Other than this you can replace the clock crystal.

The what is overclockable and isn’t data is a modified version of LSX's thread here.

Anyway, back to overclocking

Ok say you own a Pentium 2 450Mhz CPU

The number 450 is achieved from 2 factors

The multiplier and the front side bus (FSB)

So it could have a multiplier of 4.5 and a FSB of 100, the product of the multiplier and the FSB results in the final clock speed. 450MHz.

So 4.5 x 100 = 450

And a p2 500 would be 5 x 100 (this is assuming the p2 has a FSB of 100)

So if you were to change the FSB or multiplier you would then get a higher clocked CPU this is fundamentals of overclocking.

Ok so that seems simple enough, why don’t we all just naturally run overclocked computers, or computers with higher stock speeds?

Factors effecting overclocking (generated by overclocking)

More Heat as a result of:

  1. A Higher clock cycle thus more work done.
  2. An increase of power input.

And with more heat comes: A shortened life, however, depending on the voltage given and the range of the overclock, certain voltages might kill the CPU in 2 seconds, 2 weeks, 4 months or in 3 years - its generally safe or non safe, I recommend you ask experienced owners of the CPU you own so you can obtain a safe voltage without finding out the hard way.



Overclocking will make your system run faster, however small overclocks are usually hardly noticed in normal use (music, office use etc)

So it’s up to you if you want to overclock...

What overclocking effects (overclocking the CPU)

Overclocking a CPU's FSB will/can effect all of your system components, as the clock timer for the FSB also effects your AGP and PCI frequency (AGP being video card AGP = accelerated graphics port) and PCI can be anything, from sound cards, to raid cards, network cards etc, and most importantly it also effects the FSB of your RAM

Raising the multiplier effect’s only the CPU (as far as i know)

So raising the multiplier looks like a good method right? Well it is, it doesn’t effect as many components as the FSB however

  • For example:
    • On my 8RDA+ and my Athlon XP 1700+ Tbred A
    • I have multipliers from 6x - 24x and a FSB from 100-240
    • My default settings are 11x x 133FSB
    • Which equals 1466MHz
    • An maximum average overclock for my CPU is 2050Mhz (which is BIG, and WILL NOT BE THE SAME ON ALL CPUS)
    • So 2050 / 133 = 15.5
    • Simple enough I could just set my multiplier to 15.5, but I cant why?
    • Well multipliers ranging from 1 - 12.5 are 4bit multipliers while 13+ are 8bit, meaning unless I buy a CPU with an 8bit multiplier or modify my CPU to allow 8bit multipliers, I’m not going to be able to reach my maximum possible overclock
    • So at 12.5 ill need a FSB of 164
  • It gets more complicated

Well as I said before, overclocking the FSB effects almost all system components, well there are ways of preventing this, which includes:

Lockable AGP clock Lockable PCI clock FSB/RAM dividers (ram normally runs at the same FSB of that as the CPU, so if you overclock a 133 FSB to 140 the ram should be raised to 140 as well, a divider can change the amount the ram is overclocked, however ram that is in sync with the CPU FSB gives ALOT better system performance)

PCI and AGP locking is a relatively new thing on Intel p4 motherboards and Celerons, AMD Athlon XP's only just a few weeks ago got their first PCI and AGP lockable motherboard with the release of NVIDIA’s Nforce 2 Chipset

I do not recommend any other RAM divider other than 1/1 or 100%, as this gives maximum performance

And I also recommend not using multipliers to overclock, as a FSB also provides more bandwidth so overclocking the FSB not only gives better processing power but more bandwidth between the Ram, CPU and North Bridge

Ok, so you now have a clearer view of overclocking, but you still haven’t learnt what makes overclocking dangerous...

So as you’d imagine, running a CPU faster than its meant to would mean it would use more power, most motherboards allow you to change your Vcore (voltage core/ CPU voltage) so when your CPU becomes unstable, raising the voltage is sometimes the only way to make the CPU stable, however CPUS are fragile and to much Vcore can KILL a CPU, if not instantly but over time as well so its a risk you will have to take when overclocking. my CPU has a default voltage of 1.5v for a decent overclock and a good safe limit would be 1.7v for the beginner, most motherboards allow up to 1.8-1.9v as most CPUs don’t use the much power, my motherboard 8RDA+ allows up to 2.2v so if i were to run my CPU at 2.2v I would most likely instantly kill my CPU as that is a .7v increase from its default!

AMD users of the Athlon XP CPUs will find this very handy

If you are unsure of what your CPU's maximum voltage is, the manufacturer of the CPU should have somewhere on their website/manual a maximum rating for the CPU, AMD recommends a maximum of .5v which is 2.0v

But this brings up the need for very special cooling, and extreme cooling, as you are increasing the source of power, which in turn increase the heat outputted by the CPU. The stock HSF that came with the CPU was designed to work in variable conditions at the default settings, so by overclocking and greatly increasing the heat output of the CPU you will need better cooling solutions.

My CPU is currently at 1.975v at a temp of 46c using a SLK-800 heatsink with a 50CFM Sunnon fan (CFM = cubic feet moved per minute).

2v and a temp of 46c idle with a ambient of 35 is a very good temp, for an air-cooling solution, mainly because the SLK-800 is basically the beast air-cooling solution for an AMD system.

You can monitor your CPU temps using a few programs, which read probes located either inside the CPU or directly below it ones that come with your motherboard or try Motherboard Monitor.


RAM is very important when it comes to overclocking your FSB it’s important for maximum performance to keep it SYNC with your CPU FSB

RAM Quality is more important than anything, ram doesn’t generate enough heat to even need a heatsink, however if you are using a very high voltage it is recommend to add a heat-spreader to reduce temps and in term lengthen your rams life

I recommend using Samsung or Corsair XMS (Corsair is basically re-badged Samsung pick of the bunch ram which come with heat-spreaders)

RAM overclocking doesn’t require to much voltage adjustment, the default ram voltage is 2.5v for DDR, its safe to run it at 2.9v but no more or else over time you will kill your RAM!

I would recommend running your ram at 2.9v non stop as this will burn it in and over time (a few months) it will reach a higher peak overclock.


Well, this question is asked ALOT, what is a safe temperature? Or is this to high?

If you have accurate measurements, 50-55+c is much to high if you are overclocking - your average Joe with stock cooling will never notice if his CPU does get that hot, it doesn’t matter as long as your CPU is stable, temperature is almost irrelevant. I say almost because a CPU that runs at a hotter temp has a shorter life, so while it may not pay its self off as a return investment running your CPU at a cooler temp should ensure that in the time that you use your CPU you will never see it die or drop in performance.

But in the end all that matters is that your computer is stable.

When you want to compare temperatures, don’t forget to take an ambient temp at the same time, as there is always a temp difference with the CPU if the ambient is 20c compared to 35c

I recommend you check this thread out:

It’s a very nice thread which talks about temps for individual CPU's and why they can be different in certain circumstances

How to Overclock

Rule #1: take it slow!

Ok first I recommend that you find your RAM's maximum FSB.

I use a program called Memtest86, which acts as a boot disk, and outside the windows platform it rigorously tests your RAM, it tests each individual byte, over and over using different read and write patterns, this program is very highly recommended.

Get it here

Well lets get into it.

Ram overclocking

Raise your FSB slowly, while dropping your multiplier to keep the CPU at its original speed you do this so you know for sure that its the ram failing when it does

So raise the ram voltage 2.9v (assuming you are using DDR ram, if not raise your ram voltage if you can up a little not to much), and raise the FSB of the ram in 5MHz increasement, keep doing so until it doesn’t boot then drop it back say 3MHz run MEM-test with all tests, sure it takes along time, but its worth finding out your true maximum FSB from the beginning. if you receive errors, drop it back another 3MHz and keep doing so until you do not get any, then increase the FSB in 1MHz increasements until its at its most stable, yet fastest speed.

If you cannot unlock your CPU's multiplier (see below) you will have to change your ram/FSB sync in order to keep the CPU at the same clock (follow the same procedure as above)

If your ram FSB can be adjusted separately from your CPU's FSB great! Just simply raise it, and follow the steps above.

Multiplier adjustment/unlocking

While in the process of overclocking it is recommended to have the latest bios as sometimes manufactures add new features, which may benefit your overclock



Either reset to default or replace CMOS battery BEFORE flashing If you do not have a multiplier adjustable CPU the following CPUS are not multiplier adjustable:

First of all if you are not sure what type of AMD CPU you own check this OCAU thread out:

Any new Intel CPUS since Pentium 1 AMD CPUS before Athlon and Duron (is this correct?)

The Pentium 1's, and few of the Athlon Thunderbirds and the 1700+ Tbred A Athlon XP are the only CPUS you can change the multiplier without having to mod the CPU, all newer Intel CPUS are impossible to unlock

If you own an Intel p4 you may be interesting in reading up about max voltages, etc. at Intel’s posted datasheets.

AMD Duron (Spitfire) and Athlon (Thunderbird) both allow the CPU to be unlocked using a simple pencil trick which simply involves a HB pencil.

A detailed guide can be found here for unlocking the Duron spitfire and Athlon thunderbird:

If you want to unlock an Athlon XP Palimino check out these 3 guides, if you don’t like the first two guides, check out the third:

If you want to unlock an Athlon XP Tbred check this out, its easier than unlocking a Palimino (unless you own a 1700+ you lucky bugger :P)

Actual overclocking

Ok time to overclock!

But first, YOU are going to do some research on your CPU you will need to do a search, for an average overclock for your CPU (taking into consideration, the model of the CPU etc) and what cooling was used, this will help guide us to a good overclock straight off

This also means that, you will not be asking people to tell you, you will have to find it yourself, so try the PCDB for overclocks (can i get some suggestions on where else to look here please - directed at OCAU members) if you don’t it will defeat the purpose of this thread !

Ok so once you get a limitation of previous overclocks (you don’t NEED to but it helps) work out if you raise your FSB to or below the FSB and it meets that average max overclock, just do a FSB overclock, it its below, LOWER your multiplier and raise your FSB as a higher FSB is VERY good!

For e.g.

A 1700+ 1466MHz (Tbred A average overclock is 2400+ - 1950MHz (just an estimate)

11 x 133 = 1466

So say you can get your ram to 200MHz (or its DDR 400) you want it to be sync, so you would drop your multiplier to 9.5 and get your FSB to 200, however that’s only 1900MHz so you would have to raise the multiplier to 10, and use a FSB of 195

But you NEVER just start at speeds like that!

Using the gained knowledge you are now ready to begin

Drop your multiplier (if at all, if you need to raise it leave it for the moment)

and start cranking up your FSB, say 5Mhz at a time, an effective way to test (if it boots) is just play a game for a little, preferably a cpu intensive game... we don’t need to make sure its rock stable yet just a quick test to see how we are going

So keep raising until its either unstable, or wont boot, if it doesn’t boot, you will have to reset your CMOS.

You can reset the CMOS by either 1 of 2 things

Resetting CMOS

  1. Take the CMOS battery out and wait for a little, however avoid contact with the battery as getting grease on the battery from contact with your fingers will cause a chemical reaction, which gets this cool green stuff... i have no idea what it is, but its bad so don’t do it (there is only one battery, it looks like a 10c coin)
  2. Use a jumper on the motherboard to reset it this method is instant and easier than the battery method (check your motherboard manual for the jumper, if you still cant find it email the makers)

Once you get everything the way it was, try this same setting as before, however bump up the CPU voltage (Vcore) a notch and it boots or is more stable than before, continue as normal increasing the Vcore as you go along

Note: the amount of Vcore you apply and the CPU speed is a squared effect, for example, while overclocking, i got my CPU to 1860MHz at a Vcore of 1.7v, however at 1975MHz I NEED a Vcore to run it at 1.975v, so sometimes you might need to bump it up 2 notches to get it stable.

However soon you will reach a wall,

If you reach your max FSB: Try a higher multiplier, if it’s not stable try more voltage, if not, you might of hit your limit or your cooling isn’t good enough

If you reach your max voltage: sorry kiddo, you aren’t going no where, unless you modify your CPUs default voltage, go to the links reference for guides on how-to do this, if your board adds a certain amount of voltage onto the default these Mods will come in handy, if they are fixed values and are 1.850+ you will need to do a motherboard mod, which is risky, and you will have to research this yourself.

Your cooling may not be good enough: Check your temps using some monitoring software, record a log file while playing a game to see how high it gets, if it gets above 60c I would suggest a new cooling solution.

If none of the above apply or work, and you are still below the average overclock, make sure of the following things: Your using any AGP, PCI locks available, if possible set the best PCI/AGP divider possible, if this is not available, your other system components may be effecting use and unless you remove them you will not be able to get a higher FSB, so you will have to start using a higher multiplier

Refer to my section below on improving CPU temperature to see and fix your problem, even if it isn’t, I would still read it and take in a lot of it!

If all the above suggestions above cant help, your CPU may be a "bad" chip, which simply isn’t as good at overclocking as others. If possible, find out the manufacturing codes (usually printed on the IHS or around the core) and see how far others have managed to puch chips similar to yours.

So its time to do some serious stability testing, as you are going to be sitting at this speed now.

Stability testing

Games aren’t good enough to test stability, neither are benchmarking programs, we need something that purely uses ALOT of CPU power to get it done, distributed computing programs like Seti@home, prime 95 and folding at home are fine for these purposes, however if you do not use these you can download Hot CPU tester from

I recommend running these programs for hours say 12 hours, after those 12 hours and not a single crash I would say your system is stable

There’s nothing worse than a few days from now, doing something vital on your computer, and your CPU starts doing some big number crunching and your computer crashes!

During this "burn in" procedure, take note of what temperatures you are getting; also take not of what the ambient temp is (temp outside the case)

If you are getting temps of say 55c+ with an ambient close to 20c consider some cooling solutions, as when its summer or your air-con fails, you won’t be running overclocked like that!

If you are getting an ambient of say 35c, be cool, you are getting a good temp be happy!

And congrats on your overclock.

Cooling tricks and solutions

Ok, it doesn’t matter if you just want better temperatures to show off, or you need better temperatures to keep your computer stable all the following rules apply

Case air flow

If your case only has one fan moving air out and in, and that’s the PSU, I STRONGLY recommend installing 2 more case fans if possible, all cases should have a grill for at least another fan, if you will have to cut your own hole which isn’t to hard

Stock cooling = evil

  • If you are using the default heatsink which was included with your CPU/computer induce upgrade immediately!

Goto and check out the coolers and their performance

Recommended heatsinks

Both of these are GOOD performers, the only difference being the price:

  • Volcano 7+ for $50 this is bang for your buck material
  • SLK-800 $110 no fan Inc, this is an Über cooler, the BEST air cooling heatsink at the moment

(As for Intel CPUS I’m not quite sure would match the slk-800 performance wise, however the 7+ can be fitted to a p4 socket)

  • If these simply aren’t good enough, get water cooling etc.

Good watercooling kits are avaliable, as are many parts that can be mixed and matched. See the wiki entry for extreme cooling for more info.

Application methods

This area can also cause big temperature rises. The heat which moves from the CPU core to the Heatsink always has a medium of transfer in between, there are a few methods:

  • Thermal pad (solid)
  • Thermal pad (not so solid)
  • White thermal paste (generic stuff)
  • Micronized silver paste

All thermal pads are basically acceptable but they offer no real performance. If you are overclocking, or wanting a better temp it would be best to start by removing it you may ask why even sell it then? A paste, over time and pressure will be phsyically squeezed out the sides, or dry up(unlikely) so a thermal pad will stay intact while offering some thermal tranasfer and as a result is good for mass producing systems that dont need frequent maintaince (every year etc). the white paste, obviously identifiable by its white appearance, is fairly good, however, Micronized silver will give you the BEST results and isn’t expensive.

Make sure when applying your Micronized silver paste - or any paste, to only apply a VERY thing layer to the CPU core, and no layer at all on the heat sink (put some on, rub it into the metal then rub the excess, you wont be able to see it, but it fills the tiny gaps) the layer on the CPU should be very thin, so thin its transparent.

Heatsink Lapping

You can go check out this article here

or read my very brief guide on it:

  • You might need to lap your heatsink as a heatsink out of a long production line isn’t guaranteed to have a perfectly smooth mirror finish, this will effect the transfer of heat from the CPU to your heatsink.
  • So I will teach you how to lap your heatsink.
  • You will need 400, 600, 1200, 2000 grit sandpaper and something like Brasso if you want a mirror finish.
  • It’s extremely important that you do not use your hands to sand it, its recommend that you tape your sandpaper to an extremely flat surface (such as glass) this way the groves in your hands can’t effect the distribution of sanding across the heatsink base
  • Starting at 400 grit, move the heatsink in 8 motions until the entire surface has been sanded well, then move to the next grit.
  • Don’t forget to use water if you are using wet and dry
  • When using a product like Brasso is important that you clean the residue away, something like ethanol should be fine
  • You should see a mirror finish.
  • Also try a faster fan on your heatsink

Links used in article for reference

  • ALL air cooled Heatsinks benchmarked with pricing

  • AMD Athlon XP Stat sheets (maximum and extremes)

  • Ultimate bridge modding guides using an interactive interface for Athlon XP Palimino and Tbreds!

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