To test how well the K7M overclocks, I put a systems together based around an Athlon 500. Well, it's not really an Athlon 500. It has a 650 core and 3.1ns L2 cache but it was marked and sold as an Athlon 500 so I got a great deal. :-) The rest of the stuff worth talking about:

• 128 Megs Corsair PC-133 SDRAM

• Asus V6600 Deluxe GeForce 256

• Quantum 18Gig ATA/66 Hard Drive

• AMK CO-P701 cooler

• Asus 6X DVD

• SmartLink 10/100 NIC

• Diamond Monster Sound MX300

• 24" InWin Q500 case with BIG fans and other tricks

• 300 Watt power supply

The biggest problem with overclocking using the FSB is that you overclock every device in your computer in addition to the CPU. The Athlon FSB runs stock at 100Mhz, the AGP port runs at 66Mhz and the PCI runs at 33.3Mhz. To get these speed, the AMD-751 chipset divides the bus into ratios. AGP runs at 1 to 1 or 2/3 of system bus speed (2/3 of 100 = 66Mhz) and the PCI runs at 1/3 or 1/4 depending on which bus speed is selected (1/3 of 100 = 33.3Mhz). The main problem is normally with the AGP bus. Most AGP video cards will not work at 133Mhz or higher bus speed. The PCI devices don't have a problem on a 133Mhz bus speed because the divider is set to 1/4 at that speed (1/4 of 133 = 33.3Mhz).

This proved to be the case with my Asus V6600 video card. The card does not like a 133Mhz bus. It will however works on a 125Mhz bus without problem. This should give me a rock stable 625Mhz. A good 125Mhz over stock. As it turns out, the K7M chipset doesn't like working on bus speeds above 110Mhz so the highest I could get the Athlon 500 to overclock was 550Mhz.  Let's not forget that this CPU is  really a 650 so in reality it's underclocked. In order to go higher, I would need to unlocked the CPU multiplier. This is where the Free Speed Pro came in. 

One of the nice thing about the Free Speed Pro is that it allows you to adjust voltage as well as multiplier settings. Good thing too, because I hated setting those voltage jumpers! Using the Free Speed Pro and AMK CO-P701 cooler I was able to get the Athlon to run 100% stable at 800Mhz (100Mhz FSB X 8). This is quite a feat considering that the L2 cache is still set at 1/2 of core speed (stock Athlon 800 has the L2 set at 2/5 of core speed).

The K7M proved to be a very stable motherboard for the Athlon. I found the combination of K7M and Free Speed Pro almost ideal. With the two working together I can take control the two items needed to set CPU speed, bus speed and multiplier settings.

Next Page: Conclusion

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