Overclocking is the art of pushing your processor's speed faster than it is meant to run at. Most processors are overclockable, until recently, those made by Intel being the best. However, the AMD Athlon series of CPUs (Central Processing Units) are now giving Intel a run for their money.

The overall speed of your processor (500mhz for example) is achieved in two parts. The first is known as the "bus speed" and the second as "the multiplier" Multiplying the two together gives you the CPU speed, which is the speed (measured in megahertz) that your system runs at.

Example: Pentium III 500mhz, Bus Speed 100mhz, Multiplier 5. (5 X 100 = 500mhz)

Example: Celeron 433, Bus Speed 66mhz, Multiplier 6.5. (6.5 x 66 = 433)

Now, with most processors the multiplier is locked, which only leaves you the bus speed to mess about with. The way in which you alter the bus speed can be achieved either by: Reconfiguring jumpers on your motherboard, or by going into the BIOS and setting the bus speed there. (If your motherboard supports this feature)

ABIT motherboards are the most overclocking friendly and nearly always have the ability to set the bus speed in the BIOS (meaning no need to mess with the motherboard's jumpers.)

By changing this bus speed, you then change the overall speed of the processor.

Example: Pentium III 500mhz, overclocked to 560mhz. The multiplier stays at 5x, you can not change this. So you change the bus speed to 112mhz in the BIOS. The processor (CPU) now runs at 560mhz.

Every CPU is different and there are no rules on how much they overclock. Some will only give you an extra 50mhz, some an extra 400mhz! It is for you to test how far your processor will go and settle on a speed which is stable. It is extremely rare that a processor becomes damaged by overclocking but of course you do so at your own risk. (Thanks Alison for telling me what disclaimer means. Do you think my hair needs a perm?)

The best overclockers at present are as follows:

Celeron 300a: Usually overclocks to 450mhz!

Celeron 366a: Usually overclocks to 550mhz!

Athlon 500mhz: Usually overclocks to 700mhz+

If you are worried about overclocking yourself, there are stores that sell tested overclockable processors (guaranteed) for a little extra on top of the normal price.

If at first your system is not stable, you can always try increasing the cpu voltage (we do not suggest increasing this by more than 0.3 volts). This can sometimes mean the difference between a stable and an unstable system.

Good Luck! - Sarah

BY "UOAPHYS"

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Well, now that you have decided to overclock a Celeron, you will need to do a little bit of research on which one is the right chip for you (if you do not yet have one) and which motherboard you want, what type of slocket you will need, and how all this multiplier stuff works, well, here is everything you need to know:

1.1 Multipliers, Front Side Busses, and Latency

Before you even attempt to overclock, you will first need to know what a multiplier is. Well, I'll start with an example. The celeron 300a has a LOCKED multiplier of 4.5, it cannot be changed, and NO celeron's multiplier can be changed (we call this multiplier locking, not to be confused with buslocking). 

Intel started multiplier locking from back in the celeron 266 days, and has never stopped, nor will they ever stop. This is mainly because of people taking intel cpu's and overclocking them, and remarking them to sell as a higher grade cpu when in fact it is not. 

Well enough about illegal happenings, lets get back to overclocking, basically, a multiplier is what the cpu multiplies the front side bus by to get its internal cpu clock (ie 4.5 multiplier of a celeron times 66mhz front side bus(fsb) yields the celeron 300mhz cpu). 

So why are multipliers so important? Easy, a celeron 333 has a multiplier of 5, and if you try to take a 333 to 100fsb, you will have to have a cpu that is capable of 500mhz!, most celerons are good for 450, or a little bit more, but not all are capable of 500mhz+ (except the newer Celeron 366 chips which run happily at 550mhz - 100 x 5.5)... so to answer the question, how far can a 333mhz or higher celeron overclock? 

Answer, they cannot overclock to 100fsb reliably with conventional cooling (heatsink/fan no mater how large). They can however go to 75 fsb, or 83 fsb, now i will not say anything about that except that at 75 fsb, most peripherials will be fine, and at 83 fsb, there is a chance your system will become unstable.

PCI bus is one of the major factors in abnormal fsb's, this is because at any fsb under 100mhz, the pci bus has a ratio of 1/2, meaning, the pci bus will run at exactly 1/2 of the fsb, so at 83 fsb, the pci bus will have to run at ~41.5mhz! that is beyond the standard pci speed of 33mhz, which many SCSI cards and most ide hard disks cannot work without sacrificing performance such as DMA.... for any fsb over 100mhz, the PCI will run at 2/3 and up to 112fsb, is usually fine, on some motherboards, at 133fsb, the pci acutally has a 1/4 setting! :)

Memory latency is something you will also need to take into consideration. If the fastest you will go on a motherboard is 100mhz fsb, then any old pc100 sdram will work, even if it has slow latency tomshardware has a explanation of latency and memory bandwidth in its technicalities. The faster the memory is, the less latency it can have at a certain bus frequency, so CAS2 pc100 sdram can run at latency of 2 at 100fsb, and anything higher, will need latency change to CAS3. For serious overclocking (past 112 fsb) I suggest only Micron CAS2 pc100 or Samsung CAS2 pc100, both will take you to 133mhz and possibly beyond with a slightly higher latency setting...

Level 2 cache is something we all know impairs the overclockibility of most cpu's, mainly the pentium 2, and now even the new celeron 'A' with its full speed on die 128k of l2 cache. Well, right now there is only one motherboard that offers L2 latency tweaking, and that is abit. So, if you can overclock with l2 cache disabled to a certain speed, but not with it enabled, chances are a tweak in the l2 cache latency will fix it, you can set it all the way from 1(fastest) to 15(slowest but more overclockability) and default on most celerons is 5.

1.2 Motherboards, Cpu Types, and Voltages

The most common overclocking cpu is a celeron 300a (and more recently the 366), it in most cases will do 450mhz (4.5x100) and 550mhz for the 366 (5.5 x 100mhz) no problem. 

But what about all these s-specs and week numbers everyone is talking about?? Well, here are the answers. As a general rule, there are 4 basic celeron 300a's, the slot1 Retail, slot1 OEM, socket370 Retail, and socket 370 OEM. That is in no particular order, but in order of overclockbility, here it is: socket370 retail is first, very closly followed by the OEM socket370, and then comes the slot1 retail (cannot be found anymore) and the slot1 OEM's, which are still good overclockers, but just not THE best :)

So what cpu should you get? For all intents and purposes, for a celeron get the PPGA(also known as the socket 370) and if you need a motherboard, get the abit BM6 motherboard. it is capable of changing your voltage, and everything you need to do to overclock a celeron without any messy taping or soldering to get custom voltages/fsb's.

Now, the question is, should I raise my voltage to try to go faster? Well, for all intents and purposes, anything under 2.3v is fine for the celeron, and anything past that should only happen for serious overclockers who wouldn't have to ask that question in the first place. 

Voltage is a uphill battle, the more voltage you use, the more stable your cpu gets, but wait, also the more voltage, the more heat is generated, and the more heat, the less stable. So when does the voltage stability outweigh the heat instability? The only way to answer that is to try it yourself, definitely do NOT expect to get more stable past 2.3v without some serious heatsinks and fans (a big heatsink with dual fans is good, or maybe even something better :)

1.3 Cooling

Cooling is something that is stressed the MOST in overclocking, and for serious overclocking it NEEDS to be stressed. For normal overclocking a celeron 300a at 450mhz? just retail heatsink/fan will work fine at or below 2.2v usually, and an oem nice sized fan/heatsink will work a little better. 

For higher voltages you will need better cooling of course. There is a good hypothesis made by serious overclockers which says that the colder your cpu is, the faster it can overclock stably. 

This is almost a proven fact, if you can bring your cpu running temperature down 10 degrees C, you have a nice chance of a faster cpu. And as always, even more important than the heatsink on the cpu, if your case is hot instide, a 35 mile wide heatsink cannot cool the cpu.

Why? - Because blowing hot air onto a hot cpu only makes the cpu HOTTER! So general rule of thumb, if your case cools very well, then go and spend extra money on cpu heatsinks, because without great case cooling, a 50 dollar heatsink combo will do you absolutely no good.

Another way in which you can help to cool your cpu is by applying thermal grease between the processor and the heatsink.  The reason for this is that without it, there is not a solid connection between the two.  Air is not a good conductor and if there is only limited contact between the cpu and the heatsink this creates a bottleneck where heat can not dissipate freely.

By using thermal grease you create a larger surface area of contact and hence allow the heat to flow freely away from the cpu, into the heatsink and then out into the air around it.  (To then be blown out of the case by your case fans.)

HOW FAR CAN I OVERCLOCK?

Celeron 266:  Usually 448mhz (112 x 4)

Celeron 300:  Usually 450mhz (100 x 4.5)

Celeron 300a: Usually 450mhz (100 x 4.5)

Celeron 333:  Usually 415mhz (83 x 5)

Celeron 366:  Usually 550mhz (100 x 5.5)

Celeron 400:  Usually 500mhz (83 x 6)

Celeron 433:  Usually 541mhz (83 x 6.5)

Celeron 466:  Usually 525mhz (75 x 7)

Celeron 500:  Usually 560mhz (75 x 7.5)

Overclocking is an artform - Enjoy perfecting it.......