By: Sverre Sjøthun, February 18, 2002 Print this article
Ever since August of 1998, overclockers have had to face the fact that they were no longer able to manipulate the multiplier, as Intel had chosen to lock it. We have taken it upon ourselves to prove that it is in fact possible to remove this lock with even simple tools.
Before we proceed with the actual unlocking procedure, I would like to stress that this should not be performed by persons that are not familiar with overclocking. It is quite risky, and you might end up with a defective processor if you don't do it right.
Ever since August of 1998, Intel has locked the multipliers on the CPU’s. This was done to prevent unscrupulous dealers who would overclock the CPU and sell it as a higher speed processor. After fabrication and testing, the multiplier is locked on the die itself by using programmable laser-cut fuses. This is what we are going to do -- remove the fuses that the lock is consisting of. But first, let's take a look at the three states of the multiplier:
Completely unlocked: Currently, only engineering samples (ES processors) are completely unlocked. Previously, Intel processors up to the Pentium Pro, with the exception of the Pentium MMX, were completely unlocked, ie. there was no limit to the multiplier that could be applied.
Multiplier Limited: Pentium MMX and processors produced up until August 1998 were multiplier limited. They could use any multiplier up to their default multiplier. For example, a Pentium II 300MHz had a default multiplier of 4.5. You could use any multiplier up to and including 4.5, but not higher.
Multiplier Locked: All processors produced after August (week 30), 1998 are multiplier locked, ie. the multiplier can't be changed at all, regardless of motherboard settings.
With the basics of how the multiplier works in mind, it is time to start working.
Starting the procedure
Proceeding removing the lock
Tweaking the cache
Burning in the processor