by Bubba "Masterfung" Wolford

I have since built a Pentium III 450 CPU for myself and as luck would have it, my CPU was not totally stable above 504 MHz! I could get to 527MHz with the voltage pumped up to 2.2 volts but it ran too hot even with a Tenmax P3 TF special heatsink and dual fan attached.

Running an hour or more of Rogue Spear would increase my system temperature to over 105 degrees F and often cause my system to hang. Rebooting at the speed would often result in me having to reset the BIOS. Argh! Thus, I decreased the voltage to a stable 2.05 and ran my CPU at 504 MHz. This has worked much better as my temperature has dropped 10 degrees!

Before I talk about the excellent 550 MHz CPU, let me give you a run down on how different bus speeds affect CPU speeds.

Bus Speed and Multiplier

First, let me pass along this disclaimer: all CPU's are not created equal. Even getting a Malaysia Pentium III CPU off the same line as another won't guarantee the same results as another that overclocks successfully. Overclocking is often a matter of luck. However, buying a Intel PII or PIII makes the chance to hit 112 MHz bus speed very likely, though adjusting the voltage may be required.

A CPU's speed is calculated is by bus speed times the multiplier. Intel has made locked multipliers since late build 300 MHz Pentium II CPU's. However, the way around the locked multipliers is to change the bus speeds of the motherboard. Let me put down some different multipliers and bus speeds so you can see how these might impact your own attempts.

All Pentium III CPU's run on a 100 MHz bus. Pentium II CPU's 350 MHz and above run on a 100 MHz bus. Pentium II CPU's 333 MHz and below and all Celeron CPU's run on a 66 MHz bus. Let's see how this process works using Pentium III's as examples.

450 MHz Pentium III:

• 4.5 Multiplier x 100 MHz bus = 450 MHz
• 4.5 Multiplier x 103 MHz bus = 464 MHz (103 bus speed is the turbo enabled)
• 4.5 Multiplier x 112 MHz bus = 504 MHz
• 4.5 Multiplier x 117 MHz bus = 527 MHz
• 4.5 Multiplier x 124 MHz bus = 558 MHz

558 MHz is about the highest speed you can expect to hit with a stock retail Intel 450 MHz CPU. Others have reached higher speeds but these cases are very rare and often times mean disabling the cache, which as we have discussed, is not always very smart.

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However, SOME newer 450 MHz CPU's released are rumored to be 600 MHz CPU's clocked down (by multiplier) to 450 MHz. These are rumored to be reaching 600 MHz easy.

500 MHz Pentium III:

• 5.0 Multiplier x 100 bus = 500 MHz
• 5.0 Multiplier x 103 bus = 515 MHz
• 5.0 Multiplier x 112 bus = 560 MHz
• 5.0 Multiplier x 117 bus = 585 MHz

Reaching 585 MHz is about the highest CPU speed I have seen. Again, some have gotten higher but not without special cooling. One of the problems we are starting to see at these high multipliers is the limitation of the .25-micron.

550 MHz Pentium III:

• 5.5 Multiplier x 100 bus = 550 MHz
• 5.5 Multiplier x 103 bus = 567 MHz
• 5.5 Multiplier x 112 bus = 616 MHz
• 5.5 Multiplier x 117 bus = 644 MHz

Whoa! We have really eclipsed 600 MHz here. This is where I have clocked my P3 550. I noticed a huge increase in speed when I went from 567 MHz to 644 MHz. Obviously I was expecting an increase in speed, but the difference was much more dramatic than I expected.

• 6.0 Multiplier x 100 bus = 600 MHz
• 6.0 Multiplier x 103 bus = 618 MHz
• 6.0 Multiplier x 105 bus = 630 MHz
• 6.0 Multiplier x 110 bus = 660 MHz

Intel's Flagship

Well, this is the flagship Intel CPU. It is quite fast as you will see in my review. The problem with the 600 MHz Intel is that we have reached the practical peak for the overclocking performance of the CPU. Intel had originally planned not to introduce a 600 MHz CPU until Coppermine. Coppermine will introduce new CPU high speeds with lower .18 micron and along with it will come the new Camino chipset introducing a new bus speed standard of 133 MHz and the long awaited 4X AGP.

The life of the .25-micron die is used up. Most 600 MHz users have been lucky to even get the CPU to reach the 103 MHz bus speed. Reaching 110 MHz bus is considered "very lucky" as few will ever see this. Reaching a 112 MHz bus is considered by most to be "beyond the design of the micron."

Go to Part IV