Overclocking Options

All Intel CPUs are currently clock multiplier locked. However you can still adjust the Front Side Bus for now. Intel has yet to come up with a way of locking that up and bringing it to market at a low enough price (which is good for us).

This means that as long as we stick to the Pentium III-500's 5X clock multiplier setting, we can increase the clock speed by increasing the bus speed of our motherboard. Here's a look at some possible overclocked speeds that the Pentium III-500 could see when using our Abit BX6 2.0 motherboard.

5 x 100MHz = 500 MHz
5 x 103MHz = 515 MHz
5 x 112MHz = 560 MHz
5 x 117Mhz = 585 Mhz
5 x 124MHz = 620 MHz
5 x 129MHz = 645 MHz
5 x 133Mhz = 665 Mhz

The Pentium III-500's 5X multiplier give us a fairly nice speed range to play with. To do the overclocking test, I removed the stock Intel heatsink (click here to find out how to do that) and put on an Alpha P125 cooler that I got from 2CoolTek. The P125 is really a Pentium II cooler. It wasn't designed for Pentium IIIs. I modified it so it would work on the PIII-500. Click here to find out how I did that.

Here are the results of my overclocking test.

5 x 100MHz = 500 MHz - 100% stable at 2V
5 x 103MHz = 515 MHz - 100% stable at 2V
5 x 112MHz = 560 MHz - 100% stable at 2V
5 x 117Mhz = 585 Mhz - 100% stable at 2V
5 x 124MHz = 620 MHz - 100% stable at 2.2V
5 x 129MHz = 645 MHz - POST, locks just as it's about to load Windows
5 x 133Mhz = 665 Mhz - POST, Locks up  at Windows splash screen

Since this is the CPU used for Project 620, I guess it's no surprise to you that it runs at 620Mhz. :-)

The L2 cache is what prevents this CPU from running at 645Mhz as I was able to load windows and run programs at 645Mhz with the L2 cache turn off. Since the Alpha P125 is already cooling the L2 cache I don't see what else I can do to get it stable at 645Mhz with the L2 on. So why not just run at 645Mhz with the L2 cache off? Because then it'll be slower than running at 620Mhz with the L2 cache on.

I don't know if this Pentium III-500 represents what all Pentium III-500 can be overclocked to. I only have one unit for testing.  I may just have lucked out and got some really good examples (hardware sponsors tend to send their best samples).

You might also want to know what the CPU does if I didn't use an Alpha P125 cooler. Let's face it, not many of us are going to spend $50 on a heatsink and then do all the mods needed to get it to work on a Pentium III. Without the P125 the PIII-500 could run at 585Mhz at 2V, 100% stable. This is with just the stock heatsink! Not bad at all!

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