Overclocking the Athlon XP Processor

This article will in detail explain how to overclock the new AMD Athlon XP CPU with the organic packaging (XP, supposedly from eXtreme Performance).

Most of you probably already know how the multiplier works on the AMD Athlon CPU’s, but I’ll try to explain it just briefly here for the ones of you that don’t. AMD produce their CPU’s in batches of several hundred, since the process of making a processor is very advanced they don’t know from scratch which CPU will be able to run at this and that speed in MHz.

So when the processors have been manufactured they are sent to the test lab where they are being tested for which speed the reliably can run at, when that has been determined the name and speed of the processor is printed in the center piece which is called the CPU core or die, and next they use a laser to cut off all L1 bridges which where used to determine which speed the chip could run at. (When the L1 bridges are connected you can change the speed of the chip “on the fly”.) But now when they have been cut off the computer doesn’t have the ability to change the multiplier through the L1 bridges anymore, so it’s now set on the processor itself, the L3 and L4 bridges determine what speed the CPU will run at from now… (The multiplier is what determines the speed which the CPU will run at, it’s a number between 5x and 12,5x which is then multiplied by your memory FSB which is always default to 133mhz on the XP line of CPU’s, so my 1,33ghz chip has a multiplier of 10 x 133 = 1,33ghz)

As you have probably already guessed reconnecting the L1 bridges will allow you to change the multiplier given to the CPU just like AMD does when testing the chips…

But of course, you either must have a mainboard which allow changing the multiplier either inside the BIOS or by jumpers on the mainboard itself…

Shown below from left to right you have the new Athlon XP and the old Thunderbird CPU, if you have a sharp eye you will notice that the L series of bridges are different between the two (yellow dots).


On the old T-Bird all you had to do was use a regular HB pencil and draw a connection between the four L1 bridges and the lead in the pencil was enough to let current flow through and thus the CPU was identified as “unlocked” by the BIOS, you were able to change the multiplier as you wanted then.

With the XP things have changed though, it’s made of an organic material, a sort of PCB board actually, as opposed to the old T-Bird which uses chisel.

The method used by AMD to cut off the bridges hasn’t changed, they still use a laser beam, but now the laser cuts a “valley or pit” down into the CPU. What this means is that the old pencil trick will not work anymore because the resistance is increased due to the pit, (the lead connection becomes longer due to it…)

But there is more to it, if you take a multimeter and measure the resistance from one of the L1 bridges to ground you will notice that it’s lower on the XP CPU, this also contributes to the “lead trick” not to work, i.e. longer distance and less current means that there will not be enough power when you start up the CPU so that it’s identified as “unlocked” by your computers BIOS…

So what we need to do is use some sort of conductive ink which has less resistance than lead, there are different types available, on the old T-Bird the Circuit Works conductive pen with micro tip worked very good, but on the XP CPU the L1 bridges themselves are also smaller and thus the tip of the pencil becomes to large for you to be able to draw a good line between the five of them without making contact between them and thus shorting the CPU out…

What I did was use a needle to apply the ink with, so if you have such a pencil as I do just squirt some out on a needle and try to apply it on the bridges, if you don’t have one though there are better alternatives available. (Non-pencil types such as the conductive ink lacquer for example.)

That’s it, you have now unlocked your CPU, hmm but wait when I start my computer I am able to select multipliers 11x through 12,5x only, hmm a closer look on the “valleys” between the L1 contacts revealed that they are so deep that they come in contact with the wires underneath, and thus we are now shorting the CPU out by filling them with conductive ink…  

I must make a statement here and that is that my XP 1,33ghz (1500+) CPU has worked flawlessly at 1,6ghz (1900+) the last week without using the additional method below, I just can’t select multipliers lower than 11, and that’s it, but hey we don’t want to do that anyway do we eh? ;-)

Ok, so you want to “professionally” unlock your XP CPU so that all multipliers become available, from 5x all the way up to 12,5x in .5 increments? Well read on then…


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